WO2003046431A1

WO2003046431A1 - Improvements in arm elements for arms of motion picture camera support and stabilizing apparatus

Info

Publication number: WO2003046431A1
Application number: PCT/AU2002/001602
Authority: WO
Inventors: Hugo Noel Langer
Original assignee: Rig Engineering Pty. Ltd.
Priority date: 2001-11-28
Filing date: 2002-11-28
Publication date: 2003-06-05

Abstract

A safety cable (154) for an arm element (16, 18) of an arm (10) for motion picture camera support and stabilizing apparatus is located within one of the coil springs (B) in an arm element (16, 18). Spring ends (156, 158), are located at respective ends of the spring (B). The safety cable (154) has two ends, which are secured to respective spring ends (156, 158). The safety cable (154) has the form of a coil spring, the spring orientation of the safety cable (154) being opposite to that of the spring (B). An exemplary spring end (156) has an aperture (162) with a wider-diameter portion (166) and a smaller diameter portion (168), with a shoulder (170) between those portions. One end of the safety cable (154) is secured in the aperture (162) of the spring end (156), using a shanked ball swage arrangement (170).

Description

IMPROVEMENTS IN ARM ELEMENTS FOR ARMS OF MOTION PICTURE CAMERA SUPPORT AND STABILIZING APPARATUS

This invention relates to support and stabilizing apparatus for motion picture cameras.

In the United States of America in the 1970s, Garrett W. Brown designed the first of what was to become the STEADICAM (Trade Mark) range of motion picture and video camera support and stabilization apparatus. US-A-4,017,168 to Brown discloses a brace worn by a camera operator, to which is pivotally attached a pair of interconnected spring-loaded arms, the other end of which is connected to a handle adapted to be gripped by the operator, and on which a hand-held motion picture or video camera could be mounted.

Hand-held cameras became popular in motion picture production in the 1960s, lending an atmosphere of reality to productions, as the camera was freed from conventional supports such as camera dollies. However, what was gained in authenticity was often lost in picture clarity and stability, as the hand-held camera was inherently unable to be held in a stable orientation as it followed the action. The apparatus of US-A-4,017,168 was capable of producing high quality results, even when the camera operator walked or ran with the camera, because of the attendant increase in stability, particularly in stabilizing quick angular deviations along the axes of pan, tilt and roll, which previously could not be adequately controlled.

Garrett Brown's early rig, generally in accordance with US-A-4,017,168, was first used in feature film production on the late Hal Ashby's "Bound for Glory" in 1975. Brown has described how as a camera operator, using his rig on the set of that motion picture, he started off up in the air on a crane platform. Then, he 'got off and "walked" with the actor David Carradine 'across the huge camp and most of the way back, dodging kids and crowds and tent-ropes and vehicles'.

The "Bound For Glory" sequence was well received. Brown's rig was able to follow the action, while supporting the camera in a manner in which the operator's motion was not transferred to it. The "Bound For Glory" footage did not suffer from the usual hand-held image instability, but it was not until the Garrett Brown rig was used in the production of the motion picture "Rocky" (released in 1976), that the use of STEADICAM-type camera supports became a regular feature of motion picture production.

Since the 1970s, there has been almost constant development of STEADICAM- type apparatus. Core concerns have been the ability to support and stabilize heavier equipment, to cater for a range of equipment weights, and to provide an isodynamic capability. A major inconvenience for operators of STEADICAM-type apparatus has been the necessity to turn down jobs because their equipment was limited to a particular camera weight range. The equipment was either too weak, which meant that the operator would have to assist the equipment by physically holding up the load with their arms, or the equipment was too strong, which meant that a lead weight or other dead weight had to be applied, to bring the camera down to eye level and a controllable height.

As effective as present-day camera support and stabilizing apparatus is, there is only one rig currently available which permits a desirably wide range of weights to be accommodated. That rig embodies the invention disclosed in US-A-6,030,130. The apparatus described in that document requires the changing of spring canisters to accommodate the aforesaid wide range of weights.

It is an object of this invention to enable an improved arm element, or an improved arm, for camera support and stabilizing apparatus, to be produced.

The invention provides a safety cable arrangement for a spring of an arm element of an arm of a motion picture or video camera stabilizing apparatus, one end of said cable being secured to said spring at or near the other end of said spring, said cable being located within said spring, characterized in that said safety cable is formed into the shape of a spring.

The invention also provides a spring cover for an arm element of an arm of a motion picture or video camera stabilizing apparatus, characterized in that said cover acts, when the spring with which it is associated breaks, to prevent a spring portion from passing from the interior of said arm element to the exterior thereof.

The invention further provides, in an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the improvement characterized by at least one of said springs being of varying strengths relative to one or more of the others of said springs.

The invention also provides, in an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the improvement characterized by the inner or central of said springs being of weaker strength relative to one or more of the others of said springs.

The invention further provides, in an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the improvement characterized by at least one of said springs being able to stretch further, without being damaged, than one or more of the others of said springs.

The invention also provides, in an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the improvement characterized by the cable portions connecting the two outer springs to the central spring being shorter than those shown in US-A-4,208,028 and US-A- 4,394,075.

The invention further provides, in an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the improvement characterized by the bolt used in apparatus for tensioning one of said outer springs, is longer than that found in products embodying the inventions of US-A-4,208,028, and US-A-4,394,075. Embodiments of the invention, which may be preferred, will be described in detail hereinafter with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of portion of the torso of a camera operator and an arm of camera support and stabilizing apparatus;

Fig, 2 is a side elevation of the arm of Fig. 1, in a first orientation;

Fig. 3 is a side elevation of the arm of Fig. 1 in a second orientation, with the spring covers omitted; Fig. 4 is a top plan view of the arm of Figs. 1 and 2, with the outer shell of one of the spring covers omitted;

Fig. 5 is a partially-sectioned side elevation of the connection of one end of an outer spring of an arm element of the arm of Fig. 1 , to the arm element;

Fig. 6 is a partially-sectioned top plan view of the connection of the other end of the arm element spring of Fig. 5 to cable, and of the connection of a link of the arm element to a support bracket;

Fig. 7 is a partially-sectioned top plan view of a central spring of an arm element;

Fig. 8 is a plan view of a blank of an inner shell of a spring cover;

Fig. 9 is a plan view of a blank of an outer shell of a spring cover; and

Fig. 10 is an end elevation of an assembly of the inner shell of Fig. 8 and the outer shell of Fig. 9, forming a spring cover.

Before commencing a detailed description of the various embodiments of the invention, some aspects require clarification. Firstly, although the invention is concerned with motion picture and video camera support and stabilizing apparatus, it is primarily concerned with the operation of the arms in such apparatus, is more particularly concerned with the elements which comprise such an arm, and is even more particularly concerned with the springs interconnected through said elements.

Complete camera support and stabilizing apparatus is shown in the previously- mentioned prior art, such as US-A-4,017,168 and US-A-5,360,196. However, the most important features of such apparatus is the arm connecting the operator's vest and the camera mount. Exemplary prior art arms are shown in US-A- 4,208,028 (Fig. 2), US-A-4,393,075 (Fig.2), and AU-A-49336/97.

Figs. 1 to 4 are similar to some of the figures of drawings which appear in the aforementioned US-A-4,208,028 and US-A-4,394,075. Those documents also clearly show, in particular in Figs. 2 and 4, how such arms are comprised of two parallelogram arm elements connected together. As shown in those figures, in practice, each element is connected to another such element to form an arm, and that arm may be connected to an operator's vest on the one end and to the camera mount at the other end.

Also clear from US-A-4,208,028 and US-A-4,394,075 is the spring arrangement in the arm elements of the arm described in those documents. In Fig. 2 of US-A- 4,208,028 and US-A-4,394,075, there is shown a parallelogram "upper arm" arm element arrangement, with upper (2) and lower (4) links, pivotally attached to brackets 6 and 8. Tension springs 24, 26 and 32 are connected in a Z-shaped arrangement, with one end of springs 24 and 32 being connected to links 2 and 4 respectively. The other ends of springs 24, 32 are connected to spring 26 by cable sections 28, 34. Springs 24, 32 may be considered outer springs, and spring 26 may be considered to be a central spring.

The present invention, as exemplified by the arm embodiments of Figs. 1 to 10, is intended to be used, in practice to modify Cinema Products' I, II, IIIA and EFP arms, or any arms manufactured by or for other manufacturers, which are generally similar to the aforementioned Cinema Products arms. The arms according the present invention are intended to be low maintenance or no maintenance arms, which are substantially silent, lighter than convention arms of the type in question, and which are corrosion and rust free.

Turning firstly to Fig. 1 , a camera operator 12 (only part of whose torso is shown) is wearing a vest 14, to which is attached an arm 10 of camera support and stabilizing apparatus of the type discussed in detail earlier in this specification.

Turning now to Fig. 3, the arm 10 consists of a first arm element 16 and a second arm element 18, which arm elements 16, 18 are substantially similar in structure and operation. The first arm element 16 may be considered an "upper arm" arm element, from the position on the arm 30 of the operator 12 it is closest to during use, and in the same context arm element 18 may be considered to be a "forearm" arm element.

Arm element 16 has upper and lower links 20, 22 respectively, which are pivotally connected at the inner end (closer to the operator 12) to a connector hinge bracket 24, and at the outer end (further from the operator 12) are connected to upper arm medial hinge bracket 26. Hinge bracket 24 is coupled to one end of a link element 27, the other end of which is coupled to fixed support block 28, which support block 28 in use is located on, or secured to, vest 14, as shown in Fig. 1.

Upper arm medial hinge bracket 26 is coupled to forearm medial hinge bracket 32 by a hinge 34 (more recently manufactured arms have a double hinge) to form a hinged elbow 36. Bracket 32 is part of second arm element 18, which as it is substantially similar to element 16, will not be further described in terms of structure and operation. At the outer (further) end of second arm element 18 there is a camera support bracket 38, which has a camera support pin 40 thereon.

Returning to first arm element 16, the spring arrangement includes a tension spring A, one end of which is secured to link 20, the other end of which is secured to a first cable portion 42, which passes over a first pulley 44 and is attached to one end of spring B. The other end of spring B is connected to a second cable portion 46, which passes over a second pulley 48 and is connected to one end of spring C. The other end of spring C is connected to link 22. It should be noted that the trunnions 50, 52, 54, 56 which provide the means for the parallelogram shape of the element 16 to change between, for example, that shown in Fig. 2 to that shown in Fig. 3, include, in the prior art documentation, short trunnions (52, 54), that is, trunnions which do not pass all the way through the element parts which are pivotally secured together. However, Cinema

Products Inc., the producer of arms embodying the invention of US-A-4,208,028 and other United States patents, has produced versions of the arm shown generally in the drawings with four trunnions tied together with a threaded rod, that is, a tie rod, which pass all the way through.

Cinema Products Inc. also produced arms with a range of springs (A, B, C) of differing strengths. Thus, a purchaser was restricted to having Red, Blue, Green, Black or Gold springs, each with a 6.82kg to 9.08kg (151b to 201b) range in his or her arm. The weakest springs are Red springs (for the lightest cameras), and the range increases in strength to the Gold springs (for the heaviest cameras).

The present invention contemplates the provision, within the one arm element 16 (or 18, or both) of springs having different strengths. In particular, it contemplates that spring B will be less strong than spring A and/or spring C. By way of preference, the invention provided that springs A and C are each stronger than the aforementioned Cinema Products' Gold springs, and spring B is weaker than the aforementioned Gold springs. More preferably, spring A and spring C each have a spring rate stronger than in the order of 15N/mm, while spring B has a spring rate weaker than in the order of 25N/mm. More preferably, spring A and spring C each have a spring rate stronger than 15N/mm, while spring B has a spring rate weaker than 15N/mm. These respective spring strengths result from the fundamental nature of the relationship between the springs and the structure of the arm element. Spring B has more space available into which it can extend, compared to springs A and C. For that reason, it is preferred that spring B is the spring selected to cater for lighter weight cameras. Most preferably, spring B has a strength between 5N/mm and 15N/mm, which enables it to cater for such cameras. Springs A and C are able to cater for heavy weight cameras. Ideally, springs A, B and C are fabricated such that there is a gap between adjacent coils, in the relaxed state of the spring, of between 0.05mm and 1.00mm. This gap assists the manufacturing process, in that fatigue resistance treatment is able to reach and contact 100% of the surface area of the coils, both inside and outside each coil, and between adjacent coils.

It has been found that an arm including elements with spring arrangements as described, is an improvement over arms produced by Cinema Products and, since patent US-A-4,208,028 expired in 1997, arms produced by other manufacturers and embodying the invention of that patent.

Conventional arms of the general type shown in Fig. 3, in particular those produced by Cinema Products, suffer from the following problem. When the arm is elevated to its uppermost position, such as that shown in Fig. 3, or lowered ("boomed") down to its lowest position, the arm tends to lock. Reference is made in that context to column 7, line 25 of US-A-4,208,028.

In the arm 10 of Fig. 3, bumper blocks 100, 102. 104 and 106 are provided, blocks 100, 102 on arm element 16, and blocks 104, 106 on arm element 18. The blocks are preferably fabricated from a material such as aluminium or a plastics material such as Du Pont's DELRING (Registered Trade Mark), nylon or polytetrafluoroethylene.

Bumper blocks such as 100, 102, 104 and 106 have been found to prevent locking of the arm 10 in the circumstances outlined above, as they provide a resting place. It has been found that a combination of bumper blocks 100, 102, 104 and 106, with arm 10 reaching its elevated or descended position, and the central spring (spring B) coming to rest against the respective block (100, 102, 104, 106) provides the desired counter-active force. Preferably, the dimensions of the bumper blocks 100, 102, 104 and 106 should be such that the upper link 20 and the lower link 22 (both Fig. 3) do not come into contact. Desirably, there should, in the type of arm to which this application relates, be a gap of at least 9.5mm between link 20 and link 22. The arm 10 of Figs. 1 to 4 is intended to be a low maintenance arm, to that end, it is preferred that all (in use) horizontal shafts such as trunnions 50, 52, 54 and 56 be fabricated from stainless steel, and the bearings in which those shafts rotate are preferably low maintenance or no maintenance bearings, more preferably fabricated from materials such as stainless steel or hardened steel, as in the original Cinema Products arms, but with a corrosion-resistant protective coating applied to every radial and thrust load bearing. The bearings may more preferably be needle roller bearings, in modified arms, and possibly roller bearings in newly- manufactured arms.

Similarly, it is preferred that all (in use) vertical shafts, such as that rotatably connecting support block 28 and bracket 24, be fabricated from a material such as stainless steel. Preferably, all bearings engaging such vertical shafts are low maintenance or no maintenance bearings. More preferably, they are fabricated from materials such as stainless steel or hardened steel, as in the original Cinema Products arms, but with a corrosion-resistant protective coating applied to every radial and thrust load bearing. The bearings may more preferably be needle roller bearings, in modified arms, and possibly roller bearings in newly-manufactured arms.

Fig. 5 shows part of upper link 20 of arm element 16 of arm 10 of Figs. 1 to 4. In particular, Fig. 5 shows the left-hand end (as viewed in Figs. 2 and 3) of link 20, where spring A is connected thereto. Part of spring A and link 20 are shown, although it could be (generally in a mirror image) spring C and link 22. As described in US-A-4,208,028 (in particular from column 5, line 58 to column 6, line 9,) there is a means to vary the tension of the equivalent of spring A. It involves a bolt 58 with a threaded shaft 108, which bolt may be rotated clockwise or anticlockwise to increase or reduce the tension in the spring. In practice, Cinema Products has produced arms which have bolts 85mm long. It has been found that bolts even longer than 85mm may further improve the operation of such an arm, exclusive of any other changes made to the conventional arms currently available on the market. A spring end 110 is located in the end of spring A. A spring end 110 is cup shaped, with a central aperture in the "base" to allow the passage of shaft 108. Preferably, the spring end 110 is fabricated from a material such as titanium, as titanium is lightweight, corrosion-resistant and strong. A spring keeper 112, having a generally cylindrical shape, may be located on the exterior of spring A.

Preferably, a spring keeper is able to be press-fitted into place over one or both ends of the spring.

A self-lubricating internally threaded plug 114 is located within spring A, and partially within spring end 110. The internal thread of plug 114 co-operates with the external thread of shaft 108 such that rotation of the shaft will cause relative longitudinal movement of the bolt 58 and the plug 114. In that way, the spring tension of spring A may be adjusted.

Plug 114 is preferably fabricated from a material which may be a lubricating material or may be impregnated with such a material. By way of preference, the material of plug 114 may be a sintered bronze alloy (copper, tin, iron and/or carbon), more preferably with a high porosity, for example in the order of 22% by volume. Plug 114 is preferably impregnated with a synthetic oil to the point of saturation.

Aperture 116 in Fig. 5 is for location of the bearing (as discussed earlier in this specification) to support trunnion or shaft 50.

Fig. 6 is a partially-sectioned view of the right-hand end (as viewed in Fig. 4) of arm element 16, in particular bracket 24, part of upper link 20, part of spring A and pulley 44. Bracket 24 is generally U-shaped, with arms 116, 118 supporting a means for relative rotation of bracket 24 and upper link 20. That means includes a shaft 120 having end caps 122, 124. Shaft 120 is housed in a first bearing 126 located in portion 116 of link 20, and in a second bearing 128 located in portion 118. Bracket 24 also has a bearing 184 for rotatable co-operation with support block 28. Preferably, bearing 184 is a pre-lubricated bearing with seals, more preferably a stainless steel needle roller bearing. Alternatively, the bearing 184 could be a combination of some materials such as a sintered bronze self- lubricating bearing or bush, an aluminium bearing or bush with a coating of a material such as PTFE or Freelon, or could be fabricated from a ceramic material.

A spacer 130 is located between portion 118 and bearing 128, or a further bearing 132 may be located between portion 116 and bearing 126. Preferably, bearing 126 is a self-lubricating bearing or bush, or a bearing or bush formed from hardened carbon steel with a corrosion-resistant protective coating applied thereto. More preferably, bearing 126 may be a sintered bronze self-lubricating bearing or bush, or an aluminium bearing or bush with a base coated with a PTFE or Freelon surface or a ceramic material or a material such as polytetrafluoroethylene.

Bearing 128 is preferably a stainless steel needle roller bearing or an assembly of three lubricated ball bearings with seals, more preferably fabricated from stainless steel. Even more preferably, two of the ball bearings are flanged and one is not flanged. Desirably, all of the ball bearings are adapted to be press-fitted into place. By way of contrast, the equivalent bearings described in US-A-4, 158,488 (Figs. 5 and 6) have only two flanged bearings, and they are fabricated from mere carbon steel, which is prone to rusting. The two-bearing installation found in Panavision Inc. arms do not have a high enough load -bearing capacity, which is why a three-bearing arrangement has been selected to accommodate a load of approximately 584.23kg (265lb) of internal force. Furthermore, Cinema Products- installed needle roller bearings are made from hardened steel and are also prone to rusting.

Preferably, shaft 120 and spacer 130 are fabricated from stainless steel. Bearing 126 is preferably a pre-lubricated ball bearing with seals (in a new arm) or with a stainless steel needle roller thrust bearing (in an existing arm), which acts as a thrust bearing. The thrust load characteristics of the ball bearing equates to 30% of the bearing's dynamic load rating. Bearing 126 is preferably fabricated from stainless steel.

At the other end of spring A is a spring end 134 which may generally be of a similar form to spring end 110 of Fig. 5. Spring ends 110 and 134 are preferably fabricated from titanium, which is corrosion-resistant, lightweight and strong. A spring keeper 136, similar to spring keeper 112 of Fig. 5, is also located on the end of spring A.

Spring end 134 differs from spring end 110 in that instead of a single central aperture in the base of the cup shape for the passage of bolt shaft 108, it has two apertures for the attachment of cables 42, 138 which connect spring A to spring B, over pulley 44. The cables 42, 138 (which will be described in more detail in relation to Fig. 7), are attached to spring end 134 with an arrangement of a ball swage with a shank 140, 142 respectively. Preferably, the arrangements are fabricated from stainless steel.

It should be noted that the connection shown in Fig. 6 between cables 42, 138 and spring A, through spring end 136 is right at the end of spring A, unlike the arrangement in Cinema Products' arms. Cinema Products' anchor point was approximately five coils into its spring, which caused the end of the spring to drift off, and possibly to rub against the "bone" (upper link 20) and cause damage. In addition, the use of titanium makes the spring ends lighter, corrosion-resistant and stronger. The total mass of spring ends in an arm according to the present invention is less than that of a Cinema Products arm.

Pulley 44 rotates on a shaft 144, which is preferably fabricated from stainless steel. Shaft 144 is press-fitted into recesses 146, 148 in upper link 20. Preferably, the bearings or bushes 146, 148 are self-lubricating or coated metallic bearings or bushes, more preferably sintered bronze, ceramic or aluminium coated with material such as polytetrafluoroethylene. The interior of pulley 44 is provided with bearings 150, preferably with seals, and more preferably they are pre-lubricated bearings, even more preferably fabricated from stainless steel.

Fig. 7 shows spring B, isolated from the remainder of arm element 16, except for cables 42, 138 connecting spring B to spring A (see Fig. 6), and cables 46 and 152 connecting spring B to spring C (Fig. 3). In particular, Fig. 7 illustrates a safety cable 154 which prevents "shrapnel" being discharged if there is spring or cable breakage. Cinema Products' arms are provided with a safety cable (see US-A-4,208,028, column 8, line 9) located within the equivalent of spring B. However, as the main portion of the safety cable is loose within the spring, during use of the arm that portion of the cable contacts the interior surfaces of the spring, and rubs against them. As a result, a noise is produced, which is most undesirable in film-making. The Cinema Products safety cable is also prone to fatigue; it frays and protrudes from the side of the arm, thereby causing injury to persons.

In Fig. 7, the ends of spring B are provided with spring ends 156, 158, which are to all intents and purposes substantially identical. They are also similar to spring ends 110, 134 (Figs. 5 and 6), except that where spring ends 110, 134 are hollow, spring ends 156, 158 are solid. Henceforth only spring end 156 will be described, it being understood that the description of spring end 156 is applicable also to spring end 158.

Spring end 156 has three apertures (160,162, 164) therein, which apertures are generally parallel to the axis of the spring end 156. Each of apertures 160, 162, 164 has a wider-diameter portion and a smaller diameter portion, with a shoulder therebetween. These elements are exemplified in relation to aperture 162 only, with wider-diameter portion 166, smaller-diameter portion 168, and shoulder 170. Lateral apertures 160, 164 have their reduced-diameter portions located at the outer end of spring end 156, while central aperture 162 has its reduced-diameter portion at the inner end of spring end 156. Spring ends 156, 158 are preferably fabricated from titanium. Again, the total mass of spring ends in the arm of the present invention is less than those of Cinema Products' arms, and the arm of the present invention is stronger and corrosion-resistant.

Cables 42, 138 are secured to spring end 156 by having their ends captured respectively in apertures 160, 164, using the same shanked ball swage arrangement described in relation to Fig. 6. In the same way, the ends of cables 46, 152 are captured in equivalent apertures in spring end 158. Preferably, the ball swages are stainless steel and have a shank. One end of safety cable 154 is secured in aperture 162 of spring end 156 in the same manner as described for the ends of cables 42, 138 and the other end is similarly secured to spring end 156. Again, preferably, the shanked ball swages are fabricated from stainless steel. Press fit spring keepers 172, 174 are fitted to the ends of spring B. Spring keepers 172, 174 are similar to spring keepers 112, 136 of Figs. 5 and 6.

Safety cable 154 is formed into a spring. It can be seen from Fig. 7 that the spring orientation of the safety cable 154 is opposite to that of spring B. It is clear that with the expansion and contraction of spring B, the safety cable also expands and contracts, without coming into contact with the interior surfaces of spring B. In addition, the safety cable 154 is preferably sheathed in a suitable material, such as represented by a plastics coating, which mitigates against the problem existing with Cinema Products' arms, that of fraying and frayed material protruding beyond the interior of the arm.

The safety cable 154 is preferably fabricated from stainless steel. While the preferred safety cable 154 has the same strength as that used by Cinema Products, the arrangement, the shanked ball swages used by them have a breaking strength only 60% of the cable strength. The shanked ball swage arrangement of the present invention equates to a strength equal to 100% of the safety cable 154 strength. That also applies to the features 138/42 and 152/46 of Fig. 7.

Figs. 8 to 10 show aspects of spring covers 176, 178, 180 and 182 of arm 10 of Figs. 1 , 2 and 4. Spring covers 176, 178, 180, 182 may be fitted to arm elements 16, 18 of an arm 10 to protect the operator of STEADICAM-type equipment from the effects of spring breakage.

An exemplary cover such as cover 176 includes an inner shell 186 (Fig. 8) and an outer shell 188 (Fig. 9). Inner shell 186 is generally in the form of a rhombus, with a more pointed protrusion (190) at one end, and a more rounded protrusion (192) at the other end. The inner shell 186 has a central large aperture 194, which although also generally rhombus-shaped, is very nearly square in shape. Four attachment apertures 196, 198, 200, 202 are provided, for the attachment of inner shell 186 to upper link 20 of arm element 16, by way of example. Preferably, inner shell 186 is fabricated from a material, such as aluminium, which may readily be curved to a shape such as that seen in Fig. 10, for attachment to upper link 20.

By way of preferment, an inner shell 186 for use on a STEADICAM-type arm of the type discussed throughout this specification, would be about 196mm or 197mm long, with the aperture 194 being about 120mm to 122mm wide at the left-hand end (as viewed in Fig. 8) and about 119mm to 121mm at the right-hand end.

Outer shell 188 has two generally straight sides 204, 206, which are not parallel, but are nearly so. The other two sides have bights in them, giving the outer shell a waisted appearance. There are attachment apertures 208, 210, 21 , 214, which are desirably in register respectively, in use, with attachment apertures 196, 198, 200 and 202 of inner shell 176. Visible in Fig. 10 are inturned flanges 216, 218 on sides 204, 206. The flanges 216, 218 may be in the order of about 2.5mm to about 4.7mm in width. The curvature of the cover 176 as shown in Fig. 10 may have a radius of about 23.8mm.

Again, outer shell 188 is desirably fabricated from aluminium. In the cases of inner shell 176 and outer shell 178, the material from which they are fabricated is twice the thickness of that used by Cinema Products for its safety covers.

Returning to Figs. 1, 2 and 4, the arm 10 in each case has spring covers fitted to arm elements 16, 18. In Fig. 1 all four covers 176, 178, 180 and 182 are shown. In Fig. 2, covers 176, 180 are shown complete, with cover 178 showing the inner shell 228 only. Fig. 4 reflects that which is shown in Fig. 2.

In Figs. 2 and 4, attachments (such as screws, rivets, bolts or the like) are shown at 220, 222, 224 and 226. The attachment means 220, 222, 224, 226 are for use in securing inner shell 186 and outer shell 188 of spring cover 176 to upper link 20 of arm element 16, the attachment means co-operating with apertures, possibly threaded apertures (not shown) in upper link 16. The apertures in upper link 16, apertures 196, 198, 200, 202 in inner shell 186 and apertures 208, 210, 212, 214 in outer shell 188 are intended to be in register securement of the inner and outer shells 186, 188 to upper link 16, which forms the cover 176 on the upper link 16.

It is more convenient to describe the operation of spring cover 176 by describing cover 178, of which only inner shell 228 is shown in Fig. 2. If spring A should break, the end 230 of spring A will move to the right (as viewed in Fig. 2) and will become wedged between pulley 232 and one end of inner shell 228, formed by the rounded protrusion of Fig. 8. The wedging action will tend to raise point 192, given that the material of inner shell is relatively thin, which will cause point 234, on the edge of aperture 194 (Fig. 8) to move down to contact spring A, thus forming a brake on further movement of parts of the broken spring.

Of course, the safety mechanism described in relation spring A and safety cover 178 also applies to the other spring A, and to both springs C, of arm 10.

In US-A-4,208,028, it can be seen that the equivalents of springs A and C are relatively long, and the equivalent of spring B is relatively short. Spring B does not use all of the available space within the parallelogram arrangement of the equivalent of arm element 16 (or 18). In Figs. 2 and 3 of this application, springs A and C may be seen, as a preferment, as relatively shorter, and spring B may be seen as relatively longer, occupying as much as possible of the available space. This arrangement means that when the arm springs are fully tensioned and the arm, not under camera load, is in its raised position (Fig. 3) spring B is hard up against trunnion shafts 52, 54. Furthermore, it can be seen that shorter springs A and C do not come into contact with pulleys 44, 48 in that arm position and status.

In Fig. 2, spring B is backed away from trunnion shafts 52, 54. As the arm 10 comes down from the Fig. 3 position, the distance between the ends of spring B and respective trunnions 52, 54 increases. At the same time, springs A and C become closer to pulleys 44, 48. In practice when the arm is at its lowest position, and the springs are tensioned for the lightest load, the ends of springs A and C will come to within 1mm of respective pulleys 44, 48, and thus do not cause any damage, and perform optimally. In Cinema Products' product embodying the invention of US-A-4,208,028, the springs are spaced at 145mm or more apart, said distance being measured from one spring's end to the next spring's end. It has been found that a better arm is obtained, exclusive of any other changes to the Cinema Products arm, by reducing said distance by shortening the relevant cable portions.

Preferably, an embodiment of the present invention would include the three features, the relative spring strengths, the shortened cable portions and the lengthened tension-adjusting bolt. Products embodying such a preferred embodiment should be seen as modifications of Cinema Products' I, II, IIIA of EFP arms, or any arm manufactured by another party subsequent to the expiry in 1997 of US-A-4,208,028 and US-A-4,394,075, such as Glidecam or Satchler arms, or others, or as an integral part of any newly-manufactured arm. It is intended that such arms be capable of accommodating weights in the range 5.91kg to 28.64kg (131b to 631b), without changing springs, arms or, in the case of US-A-6,030,130, changing spring canisters.

It can be seen that this invention provides an improvements in arm elements for a motion picture support and stabilizing apparatus. In particular the invention provides improvements in parts of such arm elements.

The entire contents of the specifications and drawings of Australian provisional patent applications nos. PR9130, filed on 28 November 2001 , and PS2581 , filed on 28 May 2002, are hereby incorporated into the disclosure of this specification.

The claims form part of the disclosure of this specification.

Claims

1. A safety cable arrangement for a spring of an arm element of an arm of a motion picture or video camera stabilizing apparatus, one end of said cable being secured to said spring at or near the other end of said spring, said cable being located within said spring, characterized in that said safety cable is formed into the shape of a spring.

2. A safety cable arrangement according to claim 1 , characterized in that said spring shape has a diameter less than that of said spring.

3. A safety cable arrangement according to claim 1 or claim 2, characterized in that said safety cable is fabricated from stainless steel.

4. A safety cable arrangement according to any preceding claim, characterized in that said safety cable is sheathed.

5. A safety cable arrangement according to claim 4, characterized in that said sheath is formed from a plastics material.

6. A safety cable arrangement according to any preceding claim, characterized in that respective end of said cable are secured to respective spring ends located within said spring, at or near the respective ends thereof.

7. A safety cable arrangement according to claim 6, characterized in that said cable is secured to said spring ends by the use of ball swages and shafts, co-operating with respective apertures in said spring ends.

8. A safety cable arrangement according to any preceding claim, characterized in that a spring keeper is located at or near at least one end of said spring, on the exterior of said spring.

9. A spring cover for an arm element of an arm of a motion picture or video camera stabilizing apparatus, characterized in that said cover acts, when the spring with which it is associated breaks, to prevent a spring portion from passing from the interior of said arm element to the exterior thereof.

10. A spring cover according to claim 9, characterized in that said spring cover includes an inner shell and an outer shell.

11. A spring cover according to claim 9 or claim 10, characterized in that said inner shell and said outer shell are provided with at least one attachment point, which may be used to attach both said shells to said arm element.

12. A spring cover according to any one of claims 9 to 11 , characterized in that said inner shell has an aperture therein, such that said outer shell may be removed, and access to said spring obtained through said aperture.

13. A spring cover according to any one of claims 9 to 12, characterized in that each said inner and outer shell is fabricated from sheet-like material.

14. A spring cover according to claim 13, characterized in that said material is aluminium.

15. A spring cover according to any one of claims 9 to 14, characterized in that said spring cover acts, when said spring breaks, by trapping a spring portion which is being urged by another spring of said apparatus towards a pulley on said arm element, between said pulley and said inner shell, said inner shell being distorted thereby such that another portion contacts said spring portion, thus acting as a brake to motion of said portion.

16. In an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the improvement being characterized by at least one of said springs being of varying strengths relative to one or more of the others of said springs.

17. The improvement according to claim 16, characterized in that the strength of each of the two outer springs is greater than the strength of the inner of central spring.

18. The improvement according to claim 17, characterized in that each of said outer springs has a strength greater than that of Cinema Products' Gold springs, and said central or inner spring has a strength less than that of Cinema Products' Gold springs.

19. In an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the improvement being characterized by the inner or central of said springs being of weaker strength relative to one or more of the others of said springs.

20. In an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the improvement being characterized by at least one of said springs being able to stretch further, without being damaged, than one or more of the others of said springs.

21. The improvement according to claim 20, characterized in that the outer springs are shorter and stronger, and able to stretch without damage, compared to products embodying the inventions of US-A-4,208,028 and US-A-4,394,075.

22. The improvement according to claim 21 , characterized in that the central or inner spring is weaker, and may stretch further without damage, than those found in products embodying the inventions of US-A-4,208,028 and US-A- 4,394,075.

23. The improvement according to claim 21 or claim 22, characterized in that said outer springs each have a spring rate stronger than in the order of 15N/mm, while the central or inner has a spring rate weaker than in the order of 25N/mm.

24. The improvement according to claim 23, characterized in that said outer springs each have a spring rate stronger than 15N/mm, while the central or inner has a spring rate weaker than 15N/mm.

25. The improvement according to claim 24, characterized in that said outer springs each have a spring rate stronger than 15N/mm, while the central or inner has a spring rate stronger than 5N/mm but weaker than 15N/mm.

26. In an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the invention characterized by the cable portions connecting the two outer springs to the central spring being shorter than those shown in US-A- 4,208,028 and US-A-4,394,075.

26. In an arm element for the arm of a motion picture or video camera stabilizing apparatus, said arm element having a parallelogram arrangement and three springs interconnected through said arrangement, the invention characterized by the bolt used in apparatus for tensioning one of said outer springs, is longer than that found in products embodying the inventions of US-A-4,208,028, and US-A-4,394,075.