Thrust chain device with toothed sprocket having asymmetric long teeth

Abstract

The present invention relates to a thrust chain device, which comprises a thrust chain (10) including a straight portion (10a) and a curved portion (10b) along an axis and links (12) hingedly connected to the axis, a thrust chain guide (20), and a drive sprocket (1) having teeth (2) that engage with the thrust chain and contact the thrust chain at involute-shaped contact surfaces (2a) included in the teeth (2), the teeth (2) having an angle between -10° and 10° with the axis of the straight portion. The sprocket engages with the chain, defining a line of action that is offset from the hinge axis, the sprocket contacts the straight portion (10a) but not the curved portion (10b), the sprocket is rotatably mounted on an axis located opposite the center of curvature of the curved portion (10b), and the contact surface (2a) has a convex front surface that faces the straight portion (10a) when the teeth (2) are engaged, and a rear surface that faces the curved portion (10b) when the teeth (2) are engaged.

Description

[Technical Field]

[0001] The present invention relates to devices for moving loads by thrust, and more particularly to transmission assemblies used in such devices. [Background technology]

[0002] When large loads need to be moved over long distances but the available space is limited, it is known to use chain drives known as rigid chains. French Patent No. 2 786 476 filed by the applicant discloses an articulated load lifting column using a rigid chain.

[0003] The rigid chain system, or articulated rod system, allows the chain to move from a folded state that takes up less space to an unfolded state that is straight and rigid and can withstand high compressive loads.

[0004] Rigid chains have a smaller overall size in the collapsed state relative to their length in the deployed state compared to cylinder, arm, or pantograph systems.

[0005] Rigid chain systems are used, for example, in the entertainment industry to quickly move scenery or stage elements over long distances, and this type of system may also be used in manufacturing, for example, when producing high-mass products on an assembly line.

[0006] By changing the number of links in the chain, the operating range of the rigid chain can be adapted to the operating environment. Summary of the Invention [Problem to be solved by the invention]

[0007] Applicant has recognized that there is a need for a thrust chain that provides high power output, low noise and vibration, long life, and low maintenance.

[0008] The present invention aims to improve the situation described above. [Means for solving the problem]

[0009] The present application provides a thrust chain device, comprising: a thrust chain including a straight portion and a curved portion along an axis; a thrust chain guide; and a drive sprocket having teeth for engaging the thrust chain, the teeth having an involute contact surface that contacts the thrust chain and defines a line of action with the axis of the straight portion at an angle between -10° and 10°, particularly close to 0°, between the chain and the axis of the straight portion. The chain includes links hingedly connected to the axle. The line of action is offset from the hinge axes of the links. The drive sprocket contacts the straight portion and does not contact the curved portion. The drive sprocket is rotatably mounted on the axle located on the side of the thrust chain opposite the center of curvature of the curved portion. The contact surface of each tooth has a convex front face that faces the straight portion when the tooth engages and a concave rear face that faces the curved portion when the tooth engages. The convex front face occupies an angle greater than half the angle occupied by the tooth. The sprocket axis is located along the axis of the straight portion in a region between the boundary between the curved and straight portions and the maximum distance from said boundary, where the teeth exert a thrust over an angle epsilon of rotation of the sprocket, and the difference between epsilon and sigma is greater than 30° when the angle sigma from one tooth to the next equals 360° / n, where n is the number of teeth on the sprocket.

[0010] If the angle occupied by one tooth is a and the angle occupied by one rounded base separating the teeth is b, the sum of the angles of all the teeth and all the bases is equal to 360°. Thus, a + b = 360° / n, where n is the number of teeth. In prior art sprockets, contact between the teeth and the chain via the chain rollers occurs over an angle equal to a / 2. This angle is equal to 1 / 2((360° / n) - b). In a sprocket according to the invention, contact between the teeth and the chain via the chain rollers occurs over an angle greater than a / 2. This angle may exceed the value of a, but is usually equal to or less than a. In other words, the angular position of the free end of the contact surface of a tooth may be behind the tangent line between the base and the rear face of said tooth, and is generally forward of the angular position of the center of the base.

[0011] When a tooth pushes a roller of a thrust chain clockwise, the linear velocity V of the roller along the axis Z is constant. At the contact point included in the contact surface, V=w p .R i In this case, R i is the instantaneous radius or distance between the contact point and the axis of rotation of the sprocket, and w p is the instantaneous angular velocity at the contact point. If the angular velocity of the sprocket is constant, R i increases and w decreases. This is made possible by the involute profile of the front or leading edge of the tooth which forms the contact surface.

[0012] Such a device proves effective when lifting variable loads and can reduce wear. The asymmetry of each tooth corresponds to the asymmetry of the roller paths in the roller train adjacent to the sprocket on both sides of a plane passing through the sprocket's axis of rotation and perpendicular to the straight section of the thrust chain, i.e., on the side of the curve and on the opposite side of the curve. In the straight section, the distance between the axes of two consecutive rollers is constant. In the curved section, the distance between the axes of two consecutive rollers is variable. This distance increases as you move away from the sprocket, reaches a maximum value, and then decreases toward the magazine section. The increase in this distance midway through the curve adjacent to the sprocket, away from the sprocket, allows the teeth and rollers to disengage from each other while maintaining the distance between them in the curved section of the thrust chain.

[0013] Such a transmission assembly can apply a distributed force to the chain over multiple teeth at the point where the chain is guided. The force components transmitted to adjacent links other than those in the translational direction of the chain are negligible. The energy efficiency of the transmission is significantly higher than known transmissions, and for the same number of sprocket teeth, the force transmitted by the sprocket to the chain can be increased. This means that for the same pitch diameter, the sprocket can receive more torque from the motor, allowing for an increased chain load. Vibration, wear, and noise during operation are significantly reduced compared to known installations.

[0014] The sprockets engage with the rods of the thrust chain. The rods are arranged in two rows, one on the inside of the curve and the other on the outside of the curve. This changes the pitch of the push chain rods on the outside of the curve, disengaging the sprocket teeth.

[0015] In one embodiment, for example, the diameter of the inner rod is at least 20% smaller than the diameter of the outer rod to provide more space for the sprocket teeth.

[0016] In one exemplary embodiment, the diameter of the inner rod varies along the axis of said rod, for example being larger within the plate of the link and smaller in the central portion facing away from the sprocket teeth.

[0017] In one embodiment, the spacing between the rows of rods is increased to increase the length of the sprocket teeth.

[0018] The tooth length increases radially to create an evolving profile. Increasing the radial tooth length allows for an increase in the angle occupied by the leading edge of the tooth. This can be increased from an angle of a / 2 to an angle of 2a / 3 or 3a / 4, or even to an angle of a, where the leading edge occupies at least the angle of each tooth. This significant increase reduces the load carried by each tooth for the same number of teeth.

[0019] In one embodiment, the contact surface is a rolling surface.

[0020] In one embodiment, the contact surface is a sliding surface.

[0021] In one embodiment, the drive sprocket is a single sprocket. The drive sprocket may have one or more rows of teeth.

[0022] In one embodiment, multiple drive sprockets are mounted on the same shaft.

[0023] In one embodiment, the epsilon-sigma difference is greater than 34°, more preferably greater than 40°.

[0024] In one embodiment, for sprockets with up to 12 teeth, the epsilon-sigma difference is greater than 46 degrees.

[0025] In one embodiment, for sprockets with up to six teeth, the epsilon-sigma difference is greater than 49 degrees.

[0026] In one embodiment, the radial dimensions of the teeth are selected so that at least two front faces of said drive sprocket simultaneously contact the thrust chain over an angle of at least 200° for a 5-tooth sprocket, at least 250° for a 6-tooth sprocket, at least 300° for a 7-tooth sprocket, and at least 340° for an 8-tooth sprocket.

[0027] In one embodiment, the radial dimensions of the teeth are selected so that at least three front faces of the drive sprocket simultaneously contact the thrust chain through an angle of at least 20° for a 9-tooth sprocket, at least 60° for a 10- or 11-tooth sprocket, at least 140° for a 12-tooth sprocket, at least 180° for a 13-15 tooth sprocket, at least 260° for a 16-24 tooth sprocket, and at least 360° for a 25-48 tooth sprocket.

[0028] In one embodiment, the sprocket has spur teeth with between 5 and 30 teeth, which ensures good continuity of motion between the wheel and chain, reduces uncontrolled movement as it moves from tooth to tooth, and reduces vibration and associated noise.

[0029] In one embodiment, the sprockets have spur teeth with a module of 3 to 64 millimeters.

[0030] In one embodiment, the push chain includes links and rods to which the links are attached, the rods contacting the teeth, at least two teeth of the drive sprocket contacting the rods in the straight section, the number of teeth on the sprocket is at least 8 or 9, and the axes in the straight section and the axes in the curved section are in adjacent layers.

[0031] In one embodiment, the chain has links hinged to one another by rods that are mounted to rotate freely on the links of the chain, and the rotation between the gears and the rods is facilitated by friction, thereby reducing wear during use of the transmission assembly.

[0032] In one embodiment, the axis of the drive sprocket is positioned along the axis of the straight section at a distance between the lower end of the straight section and the lower end of the straight section increased by the length of the link of the push chain, preferably at a distance between the lower end of the straight section and the lower end of the straight section increased by 150% of the length of the link of the push chain.

[0033] In one embodiment, the guide for the thrust chain is located on the side of the thrust chain opposite the drive sprocket.

[0034] In one embodiment, the guide has a linear thrust chain guide surface.

[0035] In one embodiment, an additional guide is located on the outside of the curve.

[0036] In one embodiment, the convex front surface is not flat, and each tooth has a tip and a radial axis, the tip being angularly offset from the axis towards the curvature.

[0037] In one embodiment, the force applied to the thrust chain by one tooth is transferred to the next tooth over a rotational stroke of the sprocket that is greater than a / 2, preferably at least 3a / 8, more preferably at least a. The force applied to the push chain by one of the teeth is transferred to the next rotational stroke of the drive sprocket, i.e. For a 6-tooth sprocket, 40° per revolution; For a 12-tooth sprocket, 25° per revolution; For a 24-tooth sprocket, 16° per revolution; 12° per revolution for a 48-tooth sprocket; The tooth is then moved to the next tooth.

[0038] In one embodiment, at least one of the rods comprises a substantially cylindrical body and at least one ring rotatably mounted around the body so as to form a guide and / or drive roller for the chain. The roller acts as a wear part and can be quickly and easily replaced during maintenance operations without complete disassembly of the chain, thereby reducing maintenance costs.

[0039] In one embodiment, the axis of rotation of the sprocket is oriented horizontally during operation.

[0040] In one embodiment, the thrust section is straight.

[0041] The guide may include a contact surface of synthetic material.

[0042] In one embodiment, the drive sprocket has a linear bearing capacity of between 80 mm and 600 mm, or 1000 mm. Compared to known sprockets, the increase in linear bearing capacity is greater than 60% for sprockets with 5 or 6 teeth, greater than 53% for sprockets with 7 to 12 teeth, greater than 47% for sprockets with 13 to 24 teeth, and greater than 45% for sprockets with 25 to 48 teeth.

[0043] In one embodiment, the drive sprocket has an angle phi occupied by the leading flank of the teeth greater than 5 degrees, particularly for 48 teeth, preferably greater than 11 degrees, particularly for 24 teeth, more preferably greater than 23 degrees, particularly for 12 teeth, and even more preferably greater than 47 degrees, particularly for 6 teeth.

[0044] In one embodiment, the drive sprocket has a sprocket height position H between 0 and 1.5 pitches.

[0045] In one embodiment, the drive sprocket has a flange width Lj between 30 mm and 150 mm, preferably between 40 mm and 120 mm. [Brief explanation of the drawings]

[0046] Other features, details and advantages of the present invention are set forth in the following detailed description and accompanying drawings. [Figure 1] FIG. 1 is a side view of a rigid chain system according to one embodiment of the present invention with a six-tooth sprocket, with a conventional sprocket profile also shown for illustrative purposes. [Figure 2] 1 in a different angular position of the sprocket. [Figure 3] FIG. 1 is a side view of a rigid chain device having a sprocket with a leading edge occupying a first additional angle. [Figure 4] FIG. 1 is a side view of a sprocket with the leading edge occupying a second additional angle. [Figure 5] FIG. 1 is a side view of a sprocket with one tooth isolated to reveal dimensional parameters. [Figure 6] FIG. 1 is a side view of a sprocket showing the linear bearing force of the teeth and several successive positions of the teeth. [Figure 7] FIG. 4 is a side view of a rigid chain system showing sprockets, pitch, and height, where the chain flange width is larger than that of FIG. 3. [Figure 8] FIG. 1 is a side view of a rigid chain device with a 9-tooth sprocket. DETAILED DESCRIPTION OF THE INVENTION

[0047] Most of the elements contained in the accompanying drawings and the following description are known, and therefore they are used as appropriate to better understand the invention and contribute to its definition.

[0048] The profile of the sprocket that meshes with the chain is significantly different from the profiles of the two gears that mesh with each other. The chain has a cylindrical rod that makes rolling contact with the sprocket teeth. The rod is rotatably mounted so that it rotates in contact with the sprocket. The rod diameter and the distance between the axes of two consecutive rods are chain parameters that affect the sprocket. Sprockets are characterized, among other things, by the number of teeth, diameter, opening between adjacent teeth, and thrust angle. FR Patent No. 2780472 discloses a thrust chain drive with a sprocket. The sprocket is equipped with idler rollers mounted between two toothed flanges, one roller per sprocket tooth. The curved portion of the thrust chain is not fixed. The thrust force is applied to the chain axis in a direction away from the chain's translational motion.

[0049] The applicant's objective is to reduce noise, vibration and wear, thereby extending the use of push chains to areas previously using other technologies such as cables or belts.

[0050] To this end, the Applicant has studied the shortcomings of current mechanisms through incremental improvements. The sprocket and chain configuration shown in French Patent No. 3061753 proves to be beneficial in that it provides a good alignment between the line of action and the axis of the straight section. In line with this characteristic, it has been found that the symmetry of each tooth about a plane passing through the axis of rotation ensures that no geometric interference occurs between the tooth and the chain, and naturally helps to achieve the desired driving contact. Thus, the tooth following the engaged tooth gradually approaches and contacts the next roller in the chain without interfering with it, and engages it in turn.

[0051] At this stage, the applicant conducted an extensive analysis of the vibration phenomenon and determined that a large portion of the vibration was caused by the sudden separation of the sprocket profile as the load supported by the chain moved to the next tooth. Therefore, it was necessary to extend the contact time so that the load could be supported by multiple teeth simultaneously, thereby distributing the load. To achieve this, the applicant considered increasing the sprocket pitch diameter and the number of sprocket teeth, but this would increase the overall size of the sprocket, increasing the sprocket's drive torque under the same load, and would also require modifications to the motor system.

[0052] Next, the applicant considered ways to maintain the sprocket's pitch diameter and the number of teeth without changing them, and designed a system that lengthened the sprocket's teeth, allowed for asymmetry in the tooth profile, and repositioned the sprocket toward the top of the curved section. Lengthening the teeth would cause interference issues with the roller adjacent to the one the tooth next engages. Making the teeth asymmetrical would also cause interference issues. Repositioning the sprocket toward the top of the curved section would reduce the period of contact between the roller and the teeth during operation. The applicant discovered that it would be desirable to apply thrust through the sprocket's teeth while guiding the chain flange linearly along its vertical section. The curved section is guided by the sprocket's teeth without receiving thrust. It is desirable to avoid transmitting force to the guide of the curved section.

[0053] During the course of research, the applicant discovered that there is an effective area for arranging sprockets. The axis of the sprocket is positioned at the same distance from the axis of the straight portion of the chain as the axis of a conventional sprocket with the same number of teeth and pitch diameter, which cooperates with a chain of the same pitch and rollers of the same diameter. The pitch is the distance along the axis of the straight portion of the chain between the axes of two rollers of the chain, particularly between the axes of two rollers of the chain closest to the sprocket.

[0054] In FR 3061753, the lowest point of contact between the tooth and the roller is also located away from the curve. In fact, said contact point was above the curve. The axis of the sprocket 1 according to the invention is located along the axis of the straight part 10a of the chain, slightly away from the curve 10b. The lowest point of contact between the tooth 2 and the roller 171 is located away from the curve 10b. The lowest point of contact between the tooth 2 and the roller 171 is above the curve 10b (see in particular Figure 7).

[0055] The axis of the sprocket 1 according to the present invention is located along the axis of the straight portion 10a of the chain 10, between the boundary 30 separating the curved portion 10b from the straight portion 10a and a distance of more than half a pitch from said boundary 30 on the opposite side of the curved portion 10b. This distance can be between zero and 1.5 pitches. Regarding the Cartesian reference frame XYZ, X is defined as the axis parallel to the axis of rotation of the sprocket 1, Z as the translation axis of the straight portion 10a, and Y as the axis perpendicular to X and Z. In most cases, axes X and Y are horizontal, and axis Z is vertical. In other words, the axis of the sprocket 1 is located in the region between the boundary 30 separating the curved portion 10b from the straight portion 10a and a maximum distance from said boundary 30 of greater than zero but not more than 1.5 pitches, preferably half a pitch.

[0056] This distance allows the leading flank 2a, or load flank, of tooth 2 to support roller 171, located above the axis of sprocket 1, over a longer angular path. This distance also allows roller 171, located in curved portion 10b, to approach leading flank 2a of tooth 2 without interfering with the tip of the leading tooth 2 whose trailing flank 2b, or leading flank 2a, is already engaged with the leading roller 171 in the counterclockwise direction. In other words, rather than continuing its movement along straight portion 10a with a zero component in the Y-axis direction, as in the prior art, roller 171, according to the present invention, has a predetermined velocity along axis Y that is opposite to the velocity component along axis Y of the corresponding tooth 2. Leading flank 2a has a convex profile. The curvature of leading flank 2a is selected to avoid fluctuations in chain speed and engine torque. The trailing flank 2b may have a profile that is concave, partially concave and partially linear, or partially concave and partially convex. The trailing flank 2b may have a profile that is partially symmetrical with respect to the leading flank 2a near the base of the tooth 2 and partially concave away from the base of the tooth 2. In another embodiment, the profile of the trailing flank 2b is partially symmetrical with respect to the leading flank 2a away from the end of the tooth 2 and partially concave near the end of the tooth 2 (see Figures 4 and 7). The leading flank 2a, i.e., the convex front surface, occupies an angle greater than half the angle occupied by the tooth 2. The leading flank may occupy an angle greater than 5 degrees, particularly for 48 teeth. The leading flank may occupy an angle greater than 11 degrees, particularly for 24 teeth. The leading flank may occupy an angle greater than 23 degrees, particularly for 12 teeth. The leading flank may occupy an angle greater than 47 degrees, particularly for 6 teeth.

[0057] The leading flank 2a is positioned facing the straight portion 10a, and the trailing flank 2b is positioned facing the curved portion 10b. The sprocket 1 functions in compression and traction.

[0058] By bringing the transmission or curved portion 10b closer to the sprocket 1 along the axis Y, which is the axis of the straight portion, openings in the chain links can be utilized, spacing the rollers 171 apart and allowing the long tooth 2 to pass between two consecutive rollers 171. The tooth 2 is longer than the teeth of known chain sprockets, both radially and in the length of its leading flank 2a. The leading flank 2a is elongated in both the curvature distance and the overall angular size. The leading flank 2a extends over more than half the angular dimension of the tooth 2. For sprockets with six teeth, the leading edge 2a extends greater than 30° or greater than 60°, preferably between 40° and 55°. For sprockets with five teeth, the leading edge 2a extends greater than 36° or 72°, preferably between 50° and 65°. For sprockets with seven teeth, the leading flank 2a extends greater than 25° or greater than 51°, preferably between 30° and 45°. For an 8-tooth sprocket, the leading edge 2a extends over an angle of more than 22.5° or more than 45°, preferably between 28° and 40°.

[0059] Thus, when sprocket 1 rotates clockwise, tooth 2 experiences roller load for a longer period over a longer angular path at the same rotational speed. The point at which contact between tooth 2 and the corresponding roller 171 is lost is farther away from the start of the leading flank 2a of the next tooth 2. Generalizing to a sprocket 1 with n teeth, each tooth 2 occupies an angle of 360° / nb. In the simple assumption that each tooth 2 has a leading flank 2a that occupies 75% of the angle a occupied by tooth 2, the leading flank 2a is angularly expanded by 50%. If the leading flank 2a occupies 100% of the angle a occupied by tooth 2, the leading flank 2a is angularly expanded by 100% compared to the case of a symmetrical tooth. The increased angular path over which the roller is driven by tooth 2 allows for simultaneous support of two rollers on two consecutive teeth and a smooth transition from zero support to maximum support on the next tooth 2 and a smooth transition from maximum support to zero support on the departing tooth 2.

[0060] The transition can occur over an angular range of several degrees. The angular range of the transition is between 1°, preferably 5°, and the aforementioned extension value of the leading flank 2a, a / 4 for 50% extension, resulting in a gentler and smoother meshing. For vibration peaks, acceleration is reduced by at least 10-30%, velocity is reduced by at least 10-30%, and displacement is reduced by at least 60-90%, depending on the vertical and speed-related operating mode. Regarding the behavior of the sprocket 1 according to the present invention, when maintaining the same torque required by the engine for a sprocket with six teeth, it behaves in terms of vibration as a sprocket with one or two more teeth, and when maintaining the same torque required for a sprocket with 12 or more teeth, it behaves in terms of vibration as a sprocket with at least two more teeth. Furthermore, since vibration causes wear on the surfaces of the chain and sprocket, burrs on the contact surfaces are reduced, leading to a longer service life.

[0061] The thrust chain device includes an open thrust chain. Open here means a chain with no closed ends. The chain includes a straight or thrust section 10a, a magazine section 10c, and a transmission or curved section 10b between the thrust section 10a and the magazine section 10c. The device includes a push chain guide 20 in the curved section 10b. The straight section is roughly vertical, and the guide directs lateral, often horizontal, forces upward. The device includes a drive sprocket 1 with teeth 2 that engage with the thrust chain at the straight section 10a. The sprocket 1 includes one or more rows of teeth 2. The rows include teeth 2 that lie in the same plane. The device includes a storage space for the magazine section 10c. The storage space is parallel to the straight section 10a and is located on the opposite side of the center of curvature of the curved section 10b.

[0062] The drive sprocket 1 engages the thrust chain in compression or tension on the side opposite the receiving section 10c. The drive sprocket 1 contacts the thrust chain via the involute surfaces of the teeth 2, which mesh with the chain by defining a line of action with the thrust section at an angle between -10° and 10°, preferably close to 0°.

[0063] The line of action preferably has an angle between the thrust section and the guide in the range of -2° to 2°, and more preferably in the range of -1° to 1°. The force applied to the guide is reduced to a first approximation bounded by the sine of the angle and is less than 3.5% of the chain thrust. The contact surface requires less frequent maintenance due to the low friction and minimal wear on the chain from the contact surface.

[0064] As shown, the toothed sprocket 1 is mounted for rotation about an axis parallel to axis X. The chain 10 has a circular meshing surface 100 which is mounted for translation along axis Z. In this case, the term "axis" is used in its geometric sense. In the embodiment described above, the circular meshing surface 100 corresponds to the circular profile of the rod 11 in a side view. Axis X corresponds to the main direction of the drive shaft, i.e., the sprocket axis. Axis Z corresponds to the vertical direction along which the circular meshing surface 100 carried by the rod 11 moves.

[0065] The center is C n-1 , C n and C n+1 The circular mating surface 100, represented by the circle referenced , is carried either directly by the body of the rod 11 without an intervening ring, or by an intermediate member such as a roller supported by the body of the rod 11, thereby forming a drive roller.

[0066] The axis of rotation of the sprocket 1 and the axis of translation of the circular meshing surface 100 are perpendicular to each other and are spaced apart from each other by a distance equal to the pitch radius Rp.

[0067] In meshing, at least two teeth 2 of sprocket 1 contact circular meshing surface 100. Because teeth 2 are spur teeth and circular meshing surface 100 is movable in a direction perpendicular to axis X, contact occurs on a line extending along axis X. Therefore, in the plane of the drawing, contact can be shown as contact point M. The connection is a straight connection.

[0068] One of the most common methods of transmitting motion in mechanics is converting one rotational motion into another. A known method of transmission is to form a spur gear by meshing a first toothed sprocket with spur teeth with a second toothed sprocket with spur teeth, thereby converting the first rotation into a second rotation. In this specification, the above simple type of gear is used as a reference to define other types of gears. Similar technical terms may also be used to describe thrust chain gears.

[0069] In this device, the assembly converts rotational motion about axis X into translational motion along axis Z. In this respect, the device is similar to a rack and sprocket gear. However, the circular meshing surface 100 differs from the profile of a conventional rack. That is, the meshing of the profile of the teeth 2 on one side with the circular meshing surface 100 on the other side provides the gears of the device with meshing characteristics different from those of a rack and sprocket gear. In this case, the rod 11 is - forming or carrying a circular meshing surface 100 that contacts the teeth 2 of the sprocket 1, and - the function of ensuring a good connection between two plates 121 on the same link, ensuring the stability of the chain; It has two different functions:

[0070] The sprocket 1 meshes with a straight, vertical section in this case. Therefore, the movement of the rod 11 during meshing is translational at the top and rotational at the bottom. This complex translational and rotational movement distinguishes the gears of the chain 10 of the present invention from conventional systems, such as traction chain systems and bicycle drive systems, which include closed chains with curved sections wrapped around toothed pulleys or push chains in which only the straight section engages the sprocket. The sprocket 1 meshes with the surface of the straight section 10a and the surface of the curved section 10b opposite the center of curvature of the curved section 10b. The magazine section 10c is located in the storage space.

[0071] That is, the meshing of the chain 10 is different from that of conventional rack and roller chains.

[0072] The combination of complex linear and rotary shaft motions and the circular profile of the rod 11 provides the meshing of the transmission assembly 1 with high vibration performance, "low amplitude vibration", which is particularly suitable for rigid chain systems allowing high speeds, high loads, quiet operation, compact drives, or a combination thereof.

[0073] The axis Z corresponds to the line of contact along which the tangential velocity of the sprocket 1 is equal to the linear velocity of the circular meshing surface 100. Therefore, the pitch radius Rp, i.e., the distance between the line of contact and the axis of rotation of the sprocket 1, is equivalent to the pitch radius of the sprocket 1, which is equal to half the pitch diameter Dp. By analogy with a rack and sprocket gear, the line of contact can be equivalent to the pitch line of the straight section 10a of the chain 10. The pitch radius of the sprocket 1 is the distance between the axis of rotation of the sprocket 1 and the axis of the roller at the point closest to the axis of rotation, i.e., the position of the roller axis in the XY plane passing through the axis of rotation. The module m of the sprocket 1 is equal to the module m of the chain 10. The pitch p of the sprocket 1 is equal to the pitch p of the chain 10. The pitch p is defined as the arc length between two points on the pitch circle of the sprocket 1 on the same meshing flanks of two consecutive teeth 2. The relationship between the pitch p and the module m can be expressed by the following equation: p = m * Pi.

[0074] During meshing, the meshing flanks on the profile of tooth 2 come into contact with the circular meshing surface 100. In a side view, the contact of the two convex surfaces defines a tangent line, shown in the figure as contact tangent line 181. Contact tangent line 181 is shown as a dashed line. During meshing, contact point M moves along a theoretical straight line, shown as line of action 182. Mechanically, line of action 182 indicates the direction of force transmitted from one meshing member to the other through contact point M.

[0075] The line of action 182 is substantially perpendicular to the contact tangent 181. In a conventional two-tooth gear with conjugate involute profiles, the contact tangent forms a pressure angle with the direction of the center line, i.e., the line connecting the centers of both gears. Therefore, the line of action forms a pressure angle ±Pi / 2 with the direction of the center line.

[0076] In a rack and gear with conjugate involute profiles, the rack is considered to be a gear with infinite radius. The straight line that extends in the direction of the rack's translational motion and corresponds to the pitch circle of a gear with infinite radius is called the reference line or pitch line. In this case, the line of action forms a pressure angle with the reference line. Therefore, the contact tangent forms a pressure angle ±Pi / 2 with the reference line.

[0077] Whether wheel-to-wheel or rack-to-gear, teeth with conjugate involute profiles offer improved properties, especially compared to Leonardo da Vinci's original interference transmission system. First, transmission is substantially constant velocity. That is, if the speed of one gear member is constant, so is the speed of the other. Second, the pressure angle during meshing is substantially constant, within machining tolerances and the onset and termination of contact phenomena. Third, rolling contact is facilitated between the two convex surfaces without slippage. Thus, motion transmission is continuous and uniform. Furthermore, wear due to friction is limited.

[0078] To prevent the rack from becoming brittle while withstanding high forces, teeth with an involute profile are typically chamfered. In other words, the radial end of each tooth is cut off, and the tooth roots (between two teeth) are not machined all the way to their base. Therefore, the radial end of the tooth is essentially flat or rounded rather than sharply angled, and the tooth roots have a substantially corresponding female shape for similar reasons. Applying such conjugate involute profiles can also limit certain slippage phenomena. Meanwhile, the known interference that occurs at the beginning and end of contact between two conjugate teeth, also known as the forward and reverse phases, is addressed here by lowering sprocket 1 so that the forward phase occurs at the curved portion 10b of chain 10. This lowering makes it possible to limit clipping of tooth 2.

[0079] Typically, pressure angles are set based on a standard. For example, this value is nominally 20° according to European standards and 25° according to American standards. Some gears, especially older gears, have an exceptional pressure angle of 14.5°. Setting a standard value also allows gear components, such as wheels and racks, to be manufactured (machined) using a single tool. In other words, designing a gear with a non-standard pressure angle requires the design of specialized machining tools, which is complex and costly. Gears are typically designed using charts for numerous parameters, such as the number of teeth and module, and these charts are created based on the standard pressure angle. It is generally wise for engineers not to deviate from this standard.

[0080] In one embodiment of the present invention, the teeth 2 of the sprocket 1 cooperate operatively with a rod 11 having a circular meshing profile, in which case certain slippage and interference phenomena, such as in the forward and reverse phases, can be avoided.

[0081] For example, the sprocket 1 has 5 to 30 teeth 2. In this embodiment, the sprocket 1 has a wheel shape with six teeth 2. The shape of the sprocket 1 resembles that of a toothed wheel with an involute profile conjugated with a rack of pitch p. The teeth 2 have leading flanks 2a and trailing flanks 2b. The concepts of leading and trailing flanks relate to the force applied between the sprocket 1 and the chain 10. The teeth 2 are substantially pointed. The pitch radius Rp of the sprocket 1 is adjusted so that the pressure angle at the contact point is substantially zero. In this case, the pitch radius Rp is shorter than the distance corresponding to the nominal pressure angle of 20° or 25°. The value of the pitch radius Rp is selected depending on the dimensions of the components, particularly the diameter and pitch p of the rod 11. For example, the pitch p is in the range of 10 mm to 200 mm. The module m is in the range of 10 / Pi to 200 / Pimm, i.e., approximately 3 mm to 64 mm. Furthermore, R is the radius of the curved portion 10b, rg is the radius of the roller 171, and D is the diameter of a circle centered on the rotation axis of the roller 171 in the row opposite the sprocket 1 and passing through the rotation axis of the adjacent roller 171 in the row closer to the sprocket 1.

[0082] In the table below, some examples of pitch radius values ​​Rp (in millimeters) are given as a function of the pitch p (in millimeters) in the left column and the number of teeth n shown in the first row.

[0083] [Table 1]

[0084] The combinations of values ​​shown are examples of embodiments of the present invention and correspond to pressure angles whose absolute values ​​are close to zero.

[0085] Thus, the illustrated gear with teeth 2 of sprocket 1 and conjugate circular meshing surface 100 has a pressure angle alpha of substantially zero. That is, the line of action forms a substantially zero angle with the direction of translational motion of thrust portion 10a of chain 10. The line of action is substantially parallel to axis Z. The contact tangent forms a substantially right angle (pressure angle ±Pi / 2) with the direction of translational motion of thrust portion 10a of chain 10. In practice, taking into account machining tolerances, this angle is less than 5° in absolute value.

[0086] In variants, the absolute value of the pressure angle is less than the above-mentioned reference value but greater than 0. For example, the pressure angle may be in the range of -10° to 10°, or in the range of -5° to 5°, or in the range of -2° to 2°, or in the range of -1° to 1°. The contact tangent 181 then forms angles (alpha ± Pi / 2) with the direction of translational motion of the thrust portion 10a of the chain 10 in the ranges of 80° to 100°, 85° to 95°, 88° to 92°, and 89° to 91°, respectively.

[0087] In the illustrated embodiment, the spacing between the circular meshing surfaces 100 carried by the rods 11 is not limited. There is no "base" connecting one outer rod 11 to another rod 11. The movement of the teeth 2 of the sprocket 1 is not limited during meshing.

[0088] Here, the radial end of tooth 2 is theoretically sharp and is machined to be rounded during manufacturing. The radial end of tooth 2 is not cut off. According to the present invention, multiple simultaneous contacts are realized, preferably one or two more than the single contact of the prior art in order to reduce vibration and parasitic noise (see FIG. 1). Furthermore, at the top of the figure, contact point M n+1 Teeth 2 n+1 When approaching the edge of the next tooth, n and circular mating surface 100 n A new contact point M nis already established, and so on. The leading edge occupies a significant angular area, greater than half the angular area of ​​tooth 2, and although in theory it could extend beyond the angular area of ​​tooth 2, in practice the angular area of ​​tooth 2 is generally limited to facilitate the design of tooth 2. Therefore, the contact point M n+1 Teeth 2 n+1 When approaching half of the angle area, the next tooth 2 n and circular mating surface 100 n A new contact point M n is established, and so on. The force is distributed and gradually transferred to the new 2n and 100n pairs, reducing the force generated at contact point M and reducing vibration.

[0089] In the illustrated embodiment, the roots of the teeth 2 of the sprocket 1 are machined to have a substantially circular profile with a diameter equal to or greater than the diameter of the circular engaging surfaces 100. Thus, each circular engaging surface 100 is received in the root between two teeth 2 before being advanced by the downstream tooth 2, within machining tolerances.

[0090] In the embodiment described here, the rods 11 are attached loosely to the links 12 of the chain 10. This encourages rotation of the outer rod 11 relative to the meshing surfaces of the teeth 2 during meshing, reducing friction and thereby wear on the rods 11 and the teeth 2. In a variant, the rod 11 is fixedly attached to one of the two links 12 connected by the rod. In this case, if the rod 11 is in direct contact with the circular meshing surfaces 100, which are configured not to rotate, slippage will occur during meshing. However, this will make the chain 10 easier to manufacture. For example, the links 12 and the outer rods 11 may be formed as a single member or may be welded together.

[0091] In the above described arrangement, almost no radial forces of the gears are generated, and the radial forces are directed mainly in the Y direction, which allows for an additional stabilization of the chain 10 during movement and reduces the vibrations transmitted to the chain 10 by the sprocket 1, especially when moving at high speeds.

[0092] The main operating principles, and in particular the kinematics of the machine, are disclosed in French patent no. 2 786 476, to which reference is made for further details.

[0093] The chain 10 includes links 12. These links 12 are hinged to each other to form the chain 10. The chain 10 used in this device forms a motion transmission member. Hereinafter, the links 12 are referred to as a chain extending from a tail link 121 carrying a hooking plate to a head link 12 N The symbols 1 to N are used to indicate the link 12. n or link 12 n It should be noted that in this specification the term link refers to a basic mechanical pattern that is replicated along the chain 10. <n<Nとすると、リンク12 n One side of the link 12 n-1 and the other side is connected to link 12 n+1 is connected to.

[0094] During the ascent, i.e., while sprocket 1 is rotating clockwise, link 12 n belong to the magazine section 10c, the curved section 10b and the straight section 10a of the chain 10, respectively, and vice versa during descent.

[0095] The device also includes a fixed guide 20. The guide 20 forms a rolling surface for the guide roller 171 (described below). The guide 20 may include a portion of the rolling surface made of a low-wear material. The guide 20 has a first straight portion corresponding to the straight portion 10a, a second straight portion corresponding to the magazine portion 10c, and a curved portion corresponding to the curved portion 10b. The guide 20 has an outwardly directed rolling surface, and the curved portion of the guide 20 is convex. One end of the curved portion connects to the first straight portion, and the other end connects to the second straight portion smoothly, i.e., without any particular branch point. The curved portion forms a transmission member. In this embodiment, the curved portion is a semicircle with a constant radius.

[0096] When the sprocket 1 is rotated counterclockwise, the chain 10 is pushed toward the receiving magazine by each tooth 2 that is in contact with the chain 10. When the sprocket 1 is rotated clockwise, the chain 10 is pushed upward by each tooth 2 and pulled out of the magazine. There is contact at the beginning of meshing, and contact is lost at the end of meshing, and a load is applied to the straight portion 10a.

[0097] The chain 10 may be of the type disclosed in French patent No. 2 780 472, to which reference is made for further details.

[0098] The chain 10 includes a series of links 12. The links 12 are hinged around a rod 11 having a transverse axis. Each link 12 has two substantially parallel flanges, i.e., paired parallel plates 121. Each plate 121 has three through holes for receiving the hinge axes and two notches forming half holes. Each plate 121 defines a transverse active front face and a transverse active rear face. The transverse active front face and the transverse active rear face of the plate 121 are supported by the transverse active rear face of the front link plate 121 and the transverse active front face of the rear link plate 121, respectively, when the link 12 is aligned, particularly within the straight portion 10a of the chain 10. Each plate 121 is disposed in the YZ plane. One plate 121 is disposed inside the link, and the other plate 121 is attached to the outside of the link, and they are symmetrical with respect to the YZ plane. The inner plates 121 adjacent to the outer plates 121 of the same link are hinged to a common rod 11. The inner plates 121 adjacent to the outer plates 121 of adjacent links are hinged to another common rod 11. The common rods are located on opposite sides of the sprocket 1. On the sprocket 1 side, each rod 11 is alternately connected to an inner plate 121 and an outer plate 121.

[0099] At both ends of the shaft or hinge rod of the link 12, there are provided guide rollers 171. The guide rollers 171 are located outside the plate 121. The guide rollers 171 cooperate with lateral guide rails provided on the lateral flanges of the housing-forming parts of the guide 20 in the push part and the magazine part and with deflecting members in the connection parts.

[0100] For ease of understanding, the profile of a conventional tooth 200 is also shown. In FIG. 3, the profile of tooth 2 is extended to its theoretical maximum radius, referred to as the outer radius, corresponding to the intersection of the leading edge 2a and the trailing edge 2b. The maximum radius is equal to the distance between the axis of rotation of sprocket 1 and the outer surface of roller 171 in the row of rollers distal to sprocket 1. If the maximum radius were greater than this distance, interference would occur between tooth 2 and roller 171 in the row of rollers located on the opposite side of sprocket 1. In practice, a safety margin is provided. The actual radius of sprocket 1 is selected to be a distance F of a few millimeters less than the maximum radius. This avoids a sharp angle between the leading and trailing flanks 2a and 2b, which would be dangerous for the operator, and the ends of tooth 2 are rounded as shown in FIGS. 1 and 2. Another way to avoid such interference is to mount the axis of rotation of sprocket 1 close to the interface 30 between the straight and curved sections 10a and 10b. With reference to FIG. 3, it can be seen that the curved length of the leading edge 2a may be greater than 70% of the pitch radius, preferably greater than 95%, and more preferably greater than 130%.

[0101] In one embodiment, the leading edge 2a with an involute profile terminates at the intersection of a line passing through the center of the concave fillet of the next tooth 2 and the axis of rotation of the sprocket 1. This prevents tooth 2 from geometrically overlapping the next tooth, although such an overlapping configuration is possible in other examples by changing the dimensions of the chain flange along axis Z.

[0102] In fact, the maximum diameter Dmax of a sprocket according to the invention with n teeth and a chain pitch p is equal to the maximum diameter Dmax of a standard symmetrical sprocket with n / 2 teeth and a chain pitch 2p.

[0103] The length of the involute profile of tooth 2 of a sprocket 1 according to the invention having n teeth is therefore equal to the length of the involute profile of the symmetric tooth of a known sprocket having n / 2 teeth and a chain pitch 2p.

[0104] The tooth support of the sprocket 1 according to the invention is equivalent to that of a sprocket having teeth with twice the pitch and half the pitch diameter.

[0105] To understand Figures 4 to 7, the variables are specified as follows:

[0106] [Table 2]

[0107] The following table compares the triangular variables obtained according to the above formula between the meshing sprocket 1 according to the present invention and a conventional sprocket. The input parameters are the pitch p, the number of teeth n, and the radius Rci of the mid-circle between two teeth. The sprocket pitch diameter Dp and the increase delta PI in the linear bearing force PI are calculated from the input parameters between the meshing sprocket 1 according to the present invention and a conventional sprocket. The distances are expressed in mm (millimeters).

[0108] [Table 3] TIFF0007766047000004.tif245170TIFF0007766047000005.tif86170Increased bearing capacity

[0109] The above results clearly show that the bearing force of the teeth 2 of the sprocket 1 according to the present invention is greater than that of the teeth of a conventional sprocket, and therefore the number of simultaneous contacts between the teeth 2 of the sprocket 1 and the rollers 171 of the thrust chain 10 can be increased without increasing the number of teeth 2 of the sprocket 1 and therefore its pitch diameter.

[0110] In Figure 4, the tooth 2 is made as long as possible while avoiding interference with the inner row rollers 171. The increase in linear bearing capacity of the leading edge 2a is at least 60%. The linear bearing capacity can be between 80 and 1000 mm, in particular greater than 120 mm, preferably greater than 180 mm in particular for 12 teeth, or even 300 mm for 24 teeth.

[0111] In Figure 7, for a thrust chain 10 with wider roller 171 row spacing, linear support is maximized while avoiding interference with the inner roller 171 rows. The linear support of the leading edge 2a is increased by at least 80%. Increasing the distance between the roller 171 rows is effective in increasing angular support. This allows for a wider flange, improving inertia and stability. The flange width Lj is between 30mm and 150mm, preferably between 40mm and 120mm.

[0112] The applicant has identified several parameters that reflect the present invention and allow for quantitative comparison. The epsilon-sigma difference reflects the increase in unit bearing force of the tooth. The epsilon-sigma difference of sprockets according to the present invention is greater than 34°, more preferably greater than 40°. For sprockets with up to 12 teeth, the epsilon-sigma difference can be greater than 46°. For sprockets with up to 6 teeth, the epsilon-sigma difference can be greater than 49°.

[0113] FIG. 7 shows the height H, which defines the vertical position of the sprocket 1 relative to the boundary 30 between the curved and straight sections 10b and 10a. This height is between 0 and 1.5 pitches. Because the height H depends on the definitions of the parameters Lj, Dmax, and R, the involute portion of the tooth 2 can freely pass between the rollers 171, which are spaced apart by a variable pitch Pv that varies with the rotational axis movement of the flange in the curved section. The variable pitch Pv exists at least in the area enclosed by the thin diagonal rectangle in FIG. 7. The pitch is constant in the straight sections. The pitch increases from the straight sections to the curved sections, reaches a maximum at a plateau or peak, and then decreases toward the magazine section.

[0114] The transmission assembly can be in the form of a module or a multi-part assembly kit. For example, two identical chassis with identical drives can be fitted with different lengths of magazine and / or chain. Multiple chains or any link can be added or removed from the kit.

[0115] The invention is not limited to the transmission assembly and its arrangement described above merely by way of example, but encompasses all variants that can be envisaged by a person skilled in the art.

Claims

1. a thrust chain (10) including links (12) hinged to a shaft, the links (12) including a straight section (10a) and a curved section (10b) along an axis; A thrust chain guide (20); a drive sprocket (1) having teeth (2) that engage with the thrust chain (10), the teeth (2) having involute contact surfaces (2a) that contact the thrust chain (10), the teeth (2) defining a line of action that is offset from the hinge rod of the link (12) and that has an angle between -10° and 10° with the axis of the straight portion (10a); A thrust chain device comprising: The driving sprocket (1) contacts the straight portion (10a) and does not contact the curved portion (10b), The drive sprocket (1) is rotatably attached to a shaft located on the thrust chain (10) side opposite to the center of curvature of the curved portion (10b), the contact surface (2a) of each tooth (2) comprises a convex front surface facing the straight portion (10a) when the tooth (2) is engaged, and a rear surface facing the curved portion (10b) when the tooth (2) is engaged; said convex front surface subtending an angle greater than half the angle subtended by said teeth (2); the angle of said convex front surface is the angle occupied by said convex front surface when viewed from the axis of said drive sprocket (1); the axis of the drive sprocket (1) is located along the axis of the straight portion (10a) in a region between a boundary (30) between the curved portion (10b) and the straight portion (10a) and a maximum distance from the boundary (30); said tooth (2) exerts a thrust force over an angle epsilon of rotation of said drive sprocket (1), and when the angle sigma from one tooth to the next is equal to 360° / n, where n is the number of teeth on the drive sprocket (1), the difference between epsilon and sigma is greater than 30°; Thrust chain device.

2. The thrust chain (10) has a rolling or sliding surface that contacts the teeth (2), The drive sprocket (1) may be a single drive sprocket or multiple drive sprockets mounted on the same shaft; the epsilon-sigma difference is greater than 34°, more preferably greater than 40°, and even greater than 46° for drive sprockets with up to 12 teeth, and greater than 49° for drive sprockets with up to 6 teeth; 10. The apparatus of claim 1.

3. the radial dimensions of the teeth (2) are selected such that at least two front faces of the drive sprocket (1) are in simultaneous contact with the thrust chain (10) over an angle of at least 200° for a 5-tooth drive sprocket, at least 250° for a 6-tooth drive sprocket, at least 300° for a 7-tooth drive sprocket, and at least 340° for an 8-tooth drive sprocket; The radial dimensions of the teeth (2) are selected so that at least three front faces of the drive sprocket (1) simultaneously contact the thrust chain (10) through an angle of at least 20° for a 9-tooth drive sprocket, at least 60° for a 10- or 11-tooth drive sprocket, at least 140° for a 12-tooth drive sprocket, at least 180° for a 13-15-tooth drive sprocket, at least 260° for a 16-24-tooth drive sprocket, and at least 360° for a 25-48-tooth drive sprocket.

3. The device according to claim 1 or 2.

4. The drive sprocket (1) may be a single drive sprocket or multiple drive sprockets mounted on the same shaft; The device according to any one of claims 1 to 3.

5. The push chain includes links and rods to which the links are attached, the rods contacting the teeth (2), at least two teeth (2) of the drive sprocket (1) contacting the rods at the axis of the straight portion (10a), the number of teeth (2) of the drive sprocket (1) is at least 8 or 9, and the axis of the straight portion (10a) and the axis of the curved portion (10b) are in adjacent layers. The device according to any one of claims 1 to 4.

6. a guide (20) for the thrust chain (10) is disposed on the side of the thrust chain (10) opposite to the drive sprocket (1); The guide (20) has a linear thrust chain guide surface, An additional guide is arranged on the outside of the curved portion (10b). The device according to any one of claims 1 to 5.

7. the force exerted on the push chain by one of said teeth (2) is transferred to the next tooth (2) over a rotational stroke of said drive sprocket (1) of 40° per revolution for a 6-tooth drive sprocket, 25° per revolution for a 12-tooth drive sprocket, 16° per revolution for a 24-tooth drive sprocket, and 12° per revolution for a 48-tooth drive sprocket; The device according to any one of claims 1 to 6.

8. the convex front surface is not flat, each tooth (2) has a rounded tip and a radial axis, the rounded tip being angularly offset from the axis towards the curved portion (10b), and the rear surface is uneven; The device according to any one of claims 1 to 7.

9. The drive sprocket (1) has 5 to 30 involute teeth (2) and is rotatably mounted on a shaft, the thrust chain (10) has rods (11), at least one of the rods (11) engages with the drive sprocket (1), the drive sprocket (1) having spur teeth with a module m of 3 to 64 mm; An apparatus according to any one of claims 1 to 8.

10. said drive sprocket (1) having a linear bearing capacity between 80mm and 1000mm, an angle (phi) occupied by the leading edge of said teeth greater than 5 degrees, preferably greater than 11 degrees, more preferably greater than 23 degrees, a drive sprocket height position H between 0 and 1.5 pitches and a flange width Lj between 40mm and 120mm; An apparatus according to any one of claims 1 to 9.

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