Patent Description:
In small scale opto-mechanics a technique to convert rotational motion to linear motion is to use a cam path and a cam follower which is constrained within some linear guide. Typical small opto-mechanical systems include rifle scopes, telescopes, and microscopes. A common problem called backlash occurs when rotation changes from clockwise to counter-clockwise or when a cam path is designed to switch linear directions at some point in the rotation as the cam follower contacts one or the other walls of the cam path.

To solve the backlash on a purely mechanical level, the cam follower must only ever follow a single path because if the follower contacts both walls at the same time and any friction exists the follower will often bind due to an imperfect cam path or it will wear down enough in some places to the point where it will no longer be contacting both walls as it initially did. This typically means it must follow (i.e., contact) only one of the cam path's walls at all times. This can be achieved with something such as a spring forcing the follower to one side. However this proves difficult at a small scale.

Large (e.g., size of a large truck) optical systems such as high-end cosmic telescopes typically use precision servos and anti-backlash gears to solve the problem. Medium size (e.g., size of a skateboard) systems may use two eccentric bearing cam followers turned opposite each other to solve the problem. Small size (e.g., rifle scopes) systems appear to have no true solution for backlash and instead typically rely on tighter tolerances with an acceptable limit of allowed backlash.

Accordingly, there is a need for more reliable ways to avoid backlash in relatively small optical devices or other devices requiring more precise movement and positioning of components.

<CIT> describes a cam follower of which the amount of elastic deformation can be appropriately restricted with a simple configuration and which can be easily manufactured, and a lens barrel. A cam follower includes a hollow cam follower body of which a distal end is open, a first slit that is cut toward a proximal end from the distal end of the cam follower body, and a second slit that is cut toward an inner peripheral portion from an outer peripheral portion of the cam follower body in a direction orthogonal to an axis. Protruding portions are provided on both inner wall surfaces of the first slit at a distal end portion of the first slit. The protruding portions restrict deformation of the cam follower body equal to or larger than a defined amount of deformation in a radial direction. <CIT> discloses a lens barrel and an imaging device utilizing the same that includes a fixed cylinder that has a guide groove; a cam cylinder which is rotatably provided to the fixed cylinder and has a cam groove having a tapered section; and a moving lens support member that supports a moving lens and movably supports a cam follower that moves along the guide groove. The cam follower has a tapered contact section, which can be brought into contact with the tapered section of the cam groove, and is impelled radially outward by the cam follower impelling member. <CIT> describes a frame member that has a shaft where one end is inserted in a recess formed in a lens frame and a head which is provided on the other end side of the shaft that extends through a rectilinear groove and engages with a cam groove formed in a cam cylinder. The rectilinear groove is formed in a main lens barrel having a lens frame on the internal circumferential side. In the frame member, the head includes a plurality of parts disposed along a circumference around the axis of the shaft, and spaces able to change clearances between the parts. The head is configured to engage with the cam groove via the rectilinear groove.

The application, in various implementations, addresses deficiencies associated with existing backlash prevention systems. The application includes exemplary backlash prevention techniques arranged to use a barrel cam to ensure more consistent movement of certain components within a relatively small device.

This application describes exemplary auto-center barrel cam devices, systems, and method that use two oppositely tapered cam paths (e.g., a wrapped path and linear path) with a double tapered (e.g., hour-glass like shaped) cam follower which has a flexure spring between opposite tapers which is then placed on a shaft. Since both cam paths and ends of the cam follower are oppositely tapered with a spring pulling it all together, the follower always stays centered within both cam paths and will not bind due to the elastic spring compensating for the imperfect cam path walls.

In various implementations, the cam path and follower technique keeps everything centered and pulling to a common location no matter the rotational direction. It allows for looser tolerances of the cam paths and instead allows the virtual centre or center of the tapered paths to be a technical feature to control rather than the flatness and form of the usual two cam path walls.

According to the first independent claim <NUM>, an auto-center barrel cam includes an outer barrel having a first channel extending longitudinally along the outer barrel where the first channel is tapered on both a first side and second side from an inner surface to an outer surface of the outer barrel outwardly at a first angle. The cam includes an inner barrel within the outer barrel. The inner barrel has an outer surface adjacent to the inner surface of the outer barrel. The inner barrel includes a second channel extending longitudinally along the inner barrel. The second channel is tapered on both a first side and a second side from an outer surface to an inner surface of the inner barrel inwardly at a second angle. The cam includes a cam follower having a flexure part including a first section with a first surface, a second section with a second surface, and a spring section between the first section and the second section configured to pull the first section and the second section toward each other. The first section is tapered at a third angle opposite the first angle to maintain the first surface in contact with the first tapered channel of the outer barrel and the second section is tapered at a forth angle opposite the second angle to maintain the second surface in contact with the second tapered channel of the inner barrel. The flexure part is arranged to maintain the cam follower within a center of the first and second channels as the inner barrel moves in relation to the outer barrel or visa versa.

The first section and the second section may form an hour-glass like shape. The flexure part may mounted on the cam follower. The cam follower may include a connector arranged to connect the cam follower to a cam follower base. The connector may include a screw part arranged to threadable engage with the cam follower base. The cam follower may include a through hole extending from the first section to the second section. The first channel may extend longitudinally along the outer barrel in at least one of a wrapped and non-linear path. The second channel may extends longitudinally along the inner barrel in a linear path. The first angle and second angle may be between <NUM> degrees and <NUM> degrees extending from the inner surface to an outer surface of the inner barrel and outer barrel respectively. The spring section may include a helical spring.

According to the second independent claim <NUM>, an optical scope for a firearm includes an optical assembly arranged to image a target and an auto-center barrel cam that includes an outer barrel having a first channel extending longitudinally along the outer barrel where the first channel is tapered on both a first side and second side from an inner surface to an outer surface of the outer barrel outwardly at a first angle. The cam includes an inner barrel within the outer barrel. The inner barrel has an outer surface adjacent to the inner surface of the outer barrel. The inner barrel includes a second channel extending longitudinally along the inner barrel. The second channel is tapered on both a first side and a second side from an outer surface to an inner surface of the inner barrel inwardly at a second angle. The cam includes a cam follower having a flexure part including a first section with a first surface, a second section with a second surface, and a spring section between the first section and the second section configured to pull the first section and the second section toward each other. The first section is tapered at a third angle opposite the first angle to maintain the first surface in contact with the first tapered channel of the outer barrel and the second section is tapered at a forth angle opposite the second angle to maintain the second surface in contact with the second tapered channel of the inner barrel. The flexure part is arranged to maintain the cam follower within a center of the first and second channels as the inner barrel moves in relation to the outer barrel or visa versa.

According to the third independent claim <NUM>, a method for manufacturing an auto-center barrel cam includes: providing an outer barrel including a first channel extending longitudinally along the outer barrel, the first channel being tapered on both a first side and second side from an inner surface to an outer surface of the outer barrel outwardly at a first angle; providing an inner barrel within the outer barrel, the inner barrel having an outer surface adjacent to the inner surface of the outer barrel, the inner barrel including a second channel extending longitudinally along the inner barrel, the second channel being tapered on both a first side and a second side from an outer surface to an inner surface of the inner barrel inwardly at a second angle; and connecting the outer barrel to the inner barrel via a cam follower, where the cam follower includes: a flexure part having a first section with a first surface, a second section with a second surface, a spring section between the first section and the second section configured to pull the first section and the second section toward each other, the first section being tapered at a third angle opposite the first angle to maintain the first surface in contact with the first tapered channel of the outer barrel and the second section being tapered at a forth angle opposite the second angle to maintain the second surface in contact with the second tapered channel of the inner barrel; and wherein, the flexure part is arranged to maintain the cam follower within a center of the first and second channels as the inner barrel moves in relation to the outer barrel.

Any two or more of the features described in this specification, including in this summary section, may be combined to form implementations not specifically described in this specification. While aspects of the disclosure may relate to rifle scopes, telescopes, and microscopes, the discloses cam device, system, and method may be applied to any relatively small device that requires a more reliable auto-centre technique capable of reducing backlash. The techniques described herein may apply to any device and/or system that converts rotational motion to linear motion using a cam path and a cam follower constrained within some linear guide. Other types of systems, may include a laser system, milling system, surgical system, lasers, flashlights, designators, and or any system where possible shifting or backlash should be minimized.

The details of one or more implementations are set forth in the accompanying drawings and the following description.

Like reference numerals in different figures indicate like elements.

The application, in various implementations, addresses deficiencies associated with mitigating backlash in relatively small devices. The application includes exemplary devices, systems, and assemblies for providing reliable backlash prevention techniques.

Innovative aspects include two oppositely tapered cam paths (wrapped and linear) with a double tapered (hour-glass like) cam follower which has a flexure spring between opposite tapers which is then placed on a shaft that would have been the typical cam follower at this scale. Since both cam paths and ends of the cam follower are oppositely tapered with a spring pulling it all together, the follower always stays centered within both cam paths and will not bind due to the elastic spring compensating for the imperfect cam path walls.

<FIG> shows a perspective view of a barrel cam <NUM> with a dual taper cam follower <NUM>. The barrel cam includes an outer barrel <NUM> and inner barrel <NUM>. The outer barrel includes a first channel <NUM> that extends longitudinally along the outer barrel <NUM> in a non-linear, helical, and/or wrapped path. The inner barrel <NUM> includes a second channel <NUM> that extends longitudinally in a linear and/or substantially straight path along the inner barrel <NUM>. The cam follower <NUM> extends between the first channel <NUM> and second channel <NUM> and aligns and/or holds the relative position between the outer barrel <NUM> and inner barrel <NUM> while they move relative to each other.

<FIG> shows a cross-sectional view <NUM> of barrel cam <NUM> with the dual taper cam follower <NUM> of <FIG>. Cam follower <NUM> includes a dual taper flexure part <NUM> that has an upper and/or first section <NUM> and a lower and/or second section <NUM>, with a spring section <NUM> therebetween. The spring section <NUM> may include at least one helical spring and/or other spring types arranged to pull the first section <NUM> toward the second section <NUM>. Cam follower <NUM> may include a cam follower base <NUM> such that the cam follower <NUM> is connectable to the cam follower base <NUM>. The cam follower <NUM> may be connectable to the cam follower base via a threadable connection <NUM>.

The first section <NUM> may include a surface <NUM> arranged to contact a surface of channel <NUM> while the second section <NUM> may include a surface <NUM> arranged to contact a surface of the second channel <NUM>. The cam follower base <NUM> may be surrounded by inner barrel <NUM>. Cam follower <NUM> may include a through hole <NUM> arranged to allow first section <NUM> to align with second section <NUM>, with spring section <NUM> therebetween. In some implementations, first section <NUM> is tapered at a third angle opposite the first angle to maintain first surface <NUM> in contact with a surface along first tapered channel <NUM> of outer barrel <NUM> and second section <NUM> is tapered at a forth angle opposite the second angle to maintain second surface <NUM> in contact with a surface along second tapered channel <NUM> of inner barrel <NUM>.

<FIG> shows another cross-sectional view <NUM> of cam follower <NUM> and flexure part <NUM> with first section <NUM> in the wrapped cam guide path or channel <NUM> of outer barrel <NUM> and second section <NUM> in the linear cam guide path or channel <NUM> of inner barrel <NUM> such that each are tapered at opposite angles.

<FIG> shows another cross-sectional view <NUM> of wrapped cam path or channel <NUM> in outer barrel <NUM> and linear cam path or channel <NUM> in inner barrel <NUM> that are each tapered at opposite angles. Threaded receiver <NUM> may be arranged to form part of connection <NUM> when cam follower <NUM> is engaged with cam follower base <NUM>.

<FIG> shows a zoomed in view <NUM> of flexure part <NUM> of cam follower <NUM> with spring <NUM> arranged to pull first section <NUM> and second section <NUM> toward each other.

Elements or steps of different implementations described may be combined to form other implementations not specifically set forth previously. Elements or steps may be left out of the systems or processes described previously without adversely affecting their operation or the operation of the system in general. Furthermore, various separate elements or steps may be combined into one or more individual elements or steps to perform the functions described in this specification.

Claim 1:
An auto-center barrel cam (<NUM>) comprising:
an outer barrel (<NUM>) including a first channel extending longitudinally along the outer barrel, the first channel (<NUM>) being tapered on both a first side and second side from an inner surface to an outer surface of the outer barrel outwardly at a first angle;
an inner barrel (<NUM>) within the outer barrel, the inner barrel having an outer surface adjacent to the inner surface of the outer barrel, the inner barrel including a second channel (<NUM>) extending longitudinally along the inner barrel, the second channel being tapered on both a first side and a second side from an outer surface to an inner surface of the inner barrel inwardly at a second angle; and characterised in that the auto-center barrel cam further comprises
a cam follower (<NUM>) including:
a flexure part (<NUM>) having a first section (<NUM>) with a first surface, a second section (<NUM>) with a second surface, a spring section (<NUM>) between the first section and the second section configured to pull the first section and the second section toward each other, the first section being tapered at a third angle opposite the first angle to maintain the first surface in contact with a surface along the first tapered channel of the outer barrel and the second section being tapered at a forth angle opposite the second angle to maintain the second surface in contact with a surface along the second tapered channel of the inner barrel; and
wherein, the flexure part (<NUM>) is arranged to maintain the cam follower within a center of the first and second channels as the inner barrel moves in relation to the outer barrel.