Abstract:
A dolly system is disclosed, which overcomes drawbacks related to unwanted noise and jerks of prior art dolly systems. The dolly system comprises wheel assemblies ( 130 ) that have independently rotating lateral support wheels ( 132, 133 ) in combination with a center wheel ( 131 ) that interact with a continuous resilient element ( 122 ) when rolling along a rail track, without encountering any gaps or bumps and without producing squeal noise due to so-called wheel-climbing that may occur in curves along the rail track.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to and claims priority to Norwegian Patent Application Serial No. 20151356, filed Oct. 8, 2015, entitled IMPROVED DOLLY SYSTEM, the entirety of which is incorporated herein by reference. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     n/a 
     TECHNICAL FIELD 
     Camera dolly systems are used in the television (TV) and motion picture industries to support and maneuver a camera. Typically, a camera dolly comprises a platform on wheels and has an arm to raise and lower the camera. The camera dolly is generally moved by dolly operators either by a manual hands-on steering or by means of a motor remotely controlled by operators in a remote control room. 
     BACKGROUND 
     In the production of motion pictures, a motion picture camera must often be moved from one position to another. The camera movements may require a change in camera position, camera angle or camera elevation. The camera movement must be performed smoothly, as even small amounts of vibration of the camera can result in unsatisfactory filming results, due to shaky or erratic recorded images. Similar requirements must often be met in the case of TV studio productions, e.g. predefined camera movements that are to be performed along the studio floor. 
     Camera dollies and pedestals have long been used to support and move motion picture cameras. Typically, a camera dolly has four wheels or pairs of wheels on a platform or chassis having a square shaped wheel base. The wheels may be attached to the chassis via articulated legs, or the wheels may be directly pivotally attached to the chassis. The camera dolly must support and enable maneuvering of the camera with a minimum of vibration or shock, to avoid degrading the filmed image quality. Consequently, a camera dolly must be designed, manufactured and maintained with precision, and the dolly may be placed on rails or tracks on the studio floor to provide an even and smooth rolling surface. 
     Regular camera dollies roll over rail tracks that have joint cuts between rail sections perpendicular to the direction of elongation of the rail track. A drawback with this is that, at some point each wheel will roll over these joint cuts. Therefore, there are points where the wheel is only supported by cuts between two rail sections. This joint has the potential to create a bump or jerk as the wheel roll over it. As mentioned above, the dolly of a TV or motion picture camera must be very smooth otherwise the bump or jerk will be seen on the resulting recording/film. 
     A currently available solution for mitigating this drawback is micro-accurate engineering in the process of manufacturing the ends of rail sections, often using heavy and expensive metal work machinery. Typically, prior art rail sections have a solid rod that protrudes from the end of one section and a round hollow receptor in the end of the other section. These are called the male and female ends of the sections and they slot together and kept tight with a locking system. If there is any gap or if the two sections are not absolutely straight, the joints will cause slight jerks when the dolly platform wheels roll over them. To minimize this bump or jerk, much time and effort is used during the setup of the dolly system so as to ensure the camera does not feel any bump. 
     However, such prior art solutions further require rail tracks of relatively large dimensions, and when being placed on top of a studio floor, creates an obstacle protruding up to 20 cm from the floor surface. On the other hand, an immersion of such a rail track to avoid it being an obstacle would require a deep trench in the floor, which would represent a permanent damage in the floor structure, and limit the possibility mobility, for reorganizing the studio and for using the studio for other purposes than TV production. 
     Another problem with camera dollies on rail tracks is the well-known rail wheel squeal which is a noise that is generated when a dolly moves more or less rapidly along rail track curves. Needless to say, studio noise is particularly important to avoid in TV studios because of the nature of the indoor environment of reflections and small distances from sound source to sound recorders. 
     Therefore there is a need for arrangements related to a dolly system that are capable of resolving or at least mitigating at least some of the abovementioned drawbacks. 
     The prior art includes U.S. Pat. No. 6,557,775 where a dolly system is described, which has drawbacks as discussed above. 
     SUMMARY 
     In view of the above, an object of the present disclosure is to overcome or at least mitigate at least some of the drawbacks related to dolly systems. 
     This is achieved in one aspect by a dolly system a dolly system that comprises a dolly platform, a rail assembly and at least one wheel assembly. The rail assembly comprises at least one elongated rail section configured to be joined together to form a rail track. An elongated continuous resilient element, e.g. made by a rubber, is configured to be attached to the at least one rail section along the rail track. The at least one wheel assembly is configured to be attached to the dolly platform and configured to roll along the rail track on top of the elongated continuous resilient element. The wheel assembly comprises a center wheel configured to support the dolly platform in a vertical direction, z, a first lateral support wheel and a second lateral support wheel. The lateral support wheels are configured to support the dolly platform in a horizontal direction, x. The first lateral support wheel and the second lateral support wheel are arranged concentrically and on either side with respect to the center wheel. The first lateral support wheel and the second lateral support wheel have a respective radial extension, r 1 , r 2 , that are larger than a radial extension, r 0 , of the center wheel and the first lateral support wheel and the second lateral support wheel are configured to rotate independent of each other and independent of the center wheel. 
     In other words, drawbacks related to unwanted noise and jerks of prior art dolly systems are overcome by the dolly system of the present disclosure. The independently rotating lateral support wheels in combination with a center wheel interact with the continuous resilient element when rolling along the rail track, without encountering any gaps or bumps and without producing squeal noise due to so-called wheel-climbing that may occur in curves along the rail track. 
     Embodiments include those where a cross section of the continuous resilient element, perpendicular to a direction of elongation of the continuous resilient element, matches a profile of a radial cross section of the wheel assembly. 
     Embodiments include those where the elongated continuous resilient element has a length that corresponds to a length of the rail track. 
     In some embodiments, a profile of a cross section of the continuous resilient element, perpendicular to a direction of elongation of the continuous resilient element is such that, when attached to the at least one rail section, an elongated cavity is formed between the at least one rail section and the resilient element. 
     In a second aspect there is provided a rail assembly for a dolly system. The rail assembly comprises at least one elongated rail section configured to be joined together to form a rail track and an elongated continuous resilient element configured to be attached to the at least one rail section along the rail track. 
     In a third aspect there is provided a wheel assembly for a dolly system. The wheel assembly is configured to be attached to a dolly platform and configured to roll along a rail track on top of an elongated continuous resilient element. The wheel assembly comprises a center wheel configured to support the dolly platform in a vertical direction, z, a first lateral support wheel and a second lateral support wheel. The lateral support wheels are configured to support the dolly platform in a horizontal direction, x. The first lateral support wheel and the second lateral support wheel are arranged concentrically and on either side with respect to the center wheel. The first lateral support wheel and the second lateral support wheel have a respective radial extension, r1, r2, that are larger than a radial extension, r0, of the center wheel and the first lateral support wheel and the second lateral support wheel are configured to rotate independent of each other and independent of the center wheel. 
     These other aspects have various embodiments, effects and advantages that correspond to those discussed above in connection with the first aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIGS. 1 a  and 1 b    are schematically illustrated perspective views of a dolly system; 
         FIG. 2  is a view from above schematically illustrated rail track; 
         FIG. 3  schematically illustrates, in cross-section, a continuous resilient element; 
         FIG. 4  schematically illustrates, in cross-section, a wheel assembly and a rail assembly; and 
         FIG. 5  schematically illustrates, in cross-section, a wheel assembly with an attached motor. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1 a  and 1 b   , the present disclosure relates to a dolly system  100 .  FIGS. 1 a  and 1 b    are perspective views of the dolly system  100 . The dolly system  100  comprises a dolly platform  110 , a rail assembly  120  and a plurality of wheel assemblies  130 . 
     In the exemplifying embodiment of  FIGS. 1 a  and 1 b   , the dolly platform  110  is trapezoid shaped with one wheel assembly  130  mounted on the short side  161  of the trapezoid shaped dolly platform  110  and two pairs of three parted wheel assemblies  130  mounted on the long side  162  of the trapezoid shaped dolly platform  110 , respectively placed near each edge of the dolly platform  110 . 
     The rail assembly  120  comprises a plurality of elongated rail sections  121 , for example in the form of milled aluminum profiles. The elongated rail sections  121  are configured to be joined together to form a rail track  143 . Needless to say, in  FIGS. 1 a  and 1 b   , the elongated rail sections  121  are few in numbers and the rail track  143  is therefore relatively short. In fact, embodiments of a rail assembly  120  include those having only a single rail section  121 . In such embodiments, the rail track  143  is realized by such a single rail section  121 . However, in the following, the number of rail sections  121  is plural. 
       FIG. 2  illustrates, schematically, how a larger number of rail sections have been joined to form rail tracks  143  having a length L and on top of which rail tracks  143 , the dolly platform  110  is located. Moreover, in  FIG. 2  a curve  150  in the rail tracks  143  is also illustrated. 
     The rail assembly  120  further comprises an elongated continuous resilient element  122 . The continuous resilient element  122  is configured to be attached to the rail sections  121  along the rail track  143  and it may have a length that corresponds to the length, L, of the rail track  143 . The elongated continuous resilient element  122  may be made of a rubber, i.e. any appropriate synthetic or natural elastomeric polymer, which has been extruded in a suitable extrusion apparatus or manufactured in any other appropriate manner. 
     As illustrated in  FIG. 2 , long seamless tracks  143  are provided for camera dollies, the rail tracks  143  having no bumps. Moreover, the rail assembly  120  is very compact and thereby enables a less visible structure that does not form an obstacle on a floor on which it is arranged and, as discussed above, a camera mounted on the dolly platform creates no noise that may be disturbing when moving along the rail tracks  143 . 
     As  FIG. 3  and  FIG. 4  illustrate, a profile  123  of a cross section of the continuous resilient element  122 , perpendicular to a direction of elongation of the continuous resilient element  122  is such that, when attached to the rail sections  121 , an elongated cavity  124 , or “slit”, is formed between the rail sections  121  and the resilient element  122 . Such a cavity  124  may provide a certain grade of flexibility when exposed to the weight of a camera and dolly platform  110  via the wheel assemblies  130 . 
     Turning now to  FIG. 4 , a wheel assembly  130  will be described in some more detail. The wheel assembly  130  is configured to be attached to the dolly platform  110  and configured to roll along the rail track  143  on top of the elongated continuous resilient element  122 . As  FIG. 4  illustrates, the wheel assembly  130  comprises a center wheel  131  that is configured to support the dolly platform  110  in a vertical direction, z. The wheel assembly further comprises a first lateral support wheel  132  and a second lateral support wheel  133 . These first and second lateral support wheels  132 ,  133  are configured to support the dolly platform  110  in a horizontal direction, x. The first lateral support wheel  132  and the second lateral support wheel  133  are arranged concentrically and on either side with respect to the center wheel  131 . Moreover, the first lateral support wheel  132  and the second lateral support wheel  133  have a respective radial extension, r1, r2, that are larger than a radial extension, r0, of the center wheel  131  and the first lateral support wheel  132  and the second lateral support wheel  133  are configured to rotate independent of each other and independent of the center wheel  131 . 
     In other words, the wheel assembly  130  may be seen as a three-parted construction having a weight bearing center wheel and two lateral wheels that perform a “steering” function. The center wheel  131 , attached to or integrated with an axle  135 , is formed as a bar with the gravity force of a camera and dolly platform  110  acting vertically towards the top of the elongated resilient, e.g. rubber, element  122 . The two lateral support wheels  132 ,  133  are tightly but independently rotationally connected on each side of the center wheel  131 , preferably by means of a respective ball bearing  136 ,  137 . 
     As exemplified in  FIG. 4 , a profile  140  of a cross section of the continuous resilient element  122 , perpendicular to a direction of elongation of the continuous resilient element  122 , may match a profile  141  of a radial cross section of the wheel assembly  130 . That is, in such an example, the combined cross section profile  141  of the center wheel  131  and the two lateral support wheels  132 ,  133  is such that it corresponds to the cross sectional profile  140  of the continuous resilient element  122 . The two lateral support wheels  132 ,  133  provide support in the x-direction via surface sides of the continuous resilient element  122 . 
     As exemplified in  FIG. 2 , when the dolly platform  110  (comprising wheel assembly  130 ) moves along the rail track  143  into a rail curve  150 , an outer side  171  of the rail track  143  and a corresponding outer surface of the continuous resilient element  122  will be longer than an inner side  172  of the rail track  143  and a corresponding inner surface of the continuous resilient element  122 , and since the two lateral support wheels  132 ,  133  are able to rotate independently, a lateral support wheel  132 ,  133  that is in contact with the outer side  171  will travel farther than a lateral support wheel  132 ,  133  that is in contact with the inner side  172 , a distance corresponding to a difference in lengths of inner and outer surface sides of the continuous resilient element  122 . Consequently, so-called “wheel climbing” on the rail track  143  in the curve  150  creating noise in the form of rail wheel squeal will then be avoided, and no such noise will be captured by a microphone during recording using the dolly system  100 . 
       FIG. 5  illustrates an embodiment of a wheel assembly  530  that comprises a motor  501 . The motor  501  is connected and adjusted to apply a moment of force on an axle  535  of a center wheel  531  for enabling movement of a camera mounted on a dolly platform, such as the dolly platform  110  illustrated in  FIGS. 1 and 2 , along a rail track such as the rail track  143  illustrated in  FIGS. 1 and 2 . 
     It must be emphasized that the terminology “comprise/comprises” as used in this specification is chosen to specify the presence of stated features, numbers, steps or components, but does not preclude the presence or addition of one or more other functions, numbers, steps, components or groups thereof. It should also be noted that the word “a” or “an” preceding an element does not exclude the presence of a plurality thereof.