Friction shaft mechanism for tows increasing and decreasing of fiber placement machine

Abstract

A friction shaft mechanism for tows increasing and decreasing of a fiber placement machine. The mechanism comprises a friction shaft body (1), wherein the outer end of the friction shaft body (1) is sleeved with a plurality of cams (2); the friction shaft body (1) has one end provided with a compression spring (3), and the other end provided with a force bearing flange (4); and the friction shaft body (1) is sequentially and alternately sleeved with friction plates (5) and the cams (2) at intervals. The friction shaft mechanism for tows increasing and decreasing of a fiber placement machine replaces a parallel-connection type structure and metal cambered-surface type friction plates with a series-connection type structure and non-metal plane type friction plates, thereby greatly improving the service life, environmental adaptability and reliability of the friction shaft.

Description

Friction shaft mechanism for increasing or decreasing yarn in a yarn laying machine Technical Field

[0001] The present invention relates to the field of composite material laying machines, and in particular to a friction shaft mechanism for increasing or decreasing yarns in a laying machine. Background Art

[0002] The automated composite fiber placement machine (AFP) is a core industrial machine required for the placement and molding of large composite structural components in the aerospace industry. The AFP's yarn-adding / removing mechanism is the core mechanism of the AFP's end effector. The AFP is an expandable, linked mechanism, with each unit limited to twice the width of the stock material (a typical unit width is 12.7 mm). During the AFP operation, the AFP presses the stationary carbon fiber prepreg material against a rotating shaft or wheel within the AFP, using friction to pull it toward the workpiece surface. During the AFP operation, the AFP uses a cutter to precisely and reliably cut the high-speed prepreg at a predetermined point. Ensuring high output, high speed, and high reliability within a limited volume is a key challenge in AFP mechanical design. Currently, AFP mechanisms are typically implemented in two ways: direct-action cutting and rolling-action cutting. The direct-action cutting mechanism, in which the cutter moves perpendicular to the stock material's direction of motion, offers a simple mechanism, but can easily interfere with the stock material at high speeds, leading to reliability issues. The rolling shearing method uses a cutter mounted on a rotating cam. The cam's linear speed matches the prepreg's movement speed. The prepreg path is tangent to the cam's outer diameter at the shearing point. When the cutter on the cam rotates to the shearing point and intersects the prepreg, the prepreg is squeezed and severed. This method eliminates interference between the cutter and the prepreg, resulting in high output and high speed, but the mechanism is complex and difficult to implement.

[0003] Patent application number 201921276253.6 describes a carbon fiber prepreg actuating device for an automatic carbon fiber laying machine. This device is a rolling yarn cutting and increasing / decreasing mechanism that has the inherent advantages of a rolling yarn cutting and increasing / decreasing mechanism, such as high speed, high output (which can be simply increased by replacing the anvil wheel spring), and long cutter life (even if the blade curls, it can still accurately complete the yarn cutting action). However, this mechanism has the following shortcomings: the top of the tightening friction plate that generates the driving friction torque on the cam is arc-shaped and mates with the end face of the inner ring of the cam. This arc-shaped contact state is unstable, resulting in rapid wear, a short lifespan, and the inability to generate a stable and controllable driving torque. When the torque is too large, the trigger cylinder assembly may not operate, resulting in reliability issues.

[0004] Patent application number 202310268682.3 describes an integrated shearing mechanism for a resin-based fiber placement system. This mechanism utilizes the "cutting" principle of a direct-acting cutting and increasing / decreasing mechanism, severing the prepreg using a moving blade and a fixed blade that chop each other. This approach results in low cutting force and high reliability. However, this mechanism has several drawbacks: The cutting force of a direct-acting cutting mechanism is primarily provided by a pneumatic cylinder (in this patent, a spring is used to increase the cutting force). Consequently, both the cutting force and the cutting speed are limited by the cylinder's size and performance, making further improvement difficult. Even with a spring, the maximum output of this mechanism is only 1 / 3 to 1 / 2 that of a rolling cutting mechanism. This necessitates specialized materials and structures for components such as the cutter and guillotine to achieve this function within this limited cutting force. This leads to two consequences: first, wear of the cutter blade can lead to cutting failure, necessitating strict requirements for the heat treatment, machining, and grinding processes of the cutter blade, otherwise quality stability cannot be guaranteed. Second, the sharpness and life of the cutter blade are mutually exclusive parameters. The sharper the cutter, the better the high-speed yarn cutting effect, but the shorter the lifespan. Chamfering the cutter (as implemented in this patent) will extend its lifespan, but it will weaken its sharpness and reduce its high-speed cutting reliability. In short, this design sacrifices high-speed performance to improve reliability and lifespan without further improving the mechanism's output, limiting its potential for increasing productivity. Summary of the Invention

[0005] In order to solve the above technical problems, this patent modifies the friction shaft structure, changes the fit between the friction plate and the cam to a planar fit, and changes the material of the friction plate, thereby solving the stability and life problems of the friction shaft in the existing technology, reducing the fluctuation range of the friction torque of a single yarn increase or decrease unit by an order of magnitude, increasing the life by an order of magnitude, and increasing the reliable yarn cutting speed by half.

[0006] The technical solution of the present invention:

[0007] A friction shaft mechanism for increasing or decreasing yarn in a silk laying machine comprises a friction shaft body, the outer end of which is sleeved with a plurality of cams, one end of which is provided with a group of compression springs, and the other end of which is provided with a load-bearing retaining edge; friction plates and cams are sleeved on the friction shaft body in alternating order.

[0008] Furthermore, a bearing is installed inside the cam, and there is no bearing inside the friction plate, but a keyway is provided to cooperate with the key on the friction shaft body.

[0009] Furthermore, a corresponding anvil wheel is provided on the surface of one side of each cam, and the anvil wheel is pre-tightened by a compression spring; a carbon fiber prepreg cutter is arranged on each cam, and the prepreg yarn path passes between the cam and the anvil wheel.

[0010] Furthermore, a trigger cylinder is arranged on the outer side of the cam, and the trigger in the trigger cylinder is clamped into the groove on the cam.

[0011] Furthermore, the friction plate is a double-layer structure with an inner and outer layer, the inner layer is a metal core that cooperates with the key on the friction shaft body, and the outer layer is a friction consumable plate made of non-metallic material.

[0012] The present invention has the following beneficial effects compared to the prior art:

[0013] This invention replaces the existing metal arc-surface friction plate inside the spring friction shaft with the cylindrical side surface of the cam, with a non-metallic friction plate end surface rubbing against the flat surface of the cam's lateral circular ring. This significantly increases the friction area, reduces stress concentration on the friction plate, and improves component life. Compared to the arc-surface contact friction method, the flat contact friction method provides more complete contact between the friction pairs, with virtually no contact point fluctuations during one rotation, resulting in stable torque. The non-metallic friction plate not only compensates for manufacturing errors in the contact surface through its own slight deformation but also exhibits a self-lubricating effect, virtually eliminating dust, wear debris, and adhesive wear during long-term, intensive use, thus preventing cam damage. Furthermore, the non-metallic friction plate offers a stable friction coefficient that not only does not change with speed but also maintains a stable coefficient even in the presence of water on the friction surface, significantly improving the mechanism's environmental adaptability. In this scenario, where cam damage is no longer a concern, the primary cause of friction shaft life reduction is friction plate wear. As the friction plate thins, the compression spring that generates the friction torque gradually lengthens, causing the friction torque to decay. The present invention relocates the spring on the friction shaft from inside the cam to the side of the friction shaft, increasing available space. This allows for the use of longer, lower-rigidity springs, significantly reducing the rate of friction torque decay for the same amount of wear. Furthermore, the spring friction shaft of the present invention is installed in series, significantly reducing disassembly compared to existing technologies, facilitating easy replacement of consumables, and improving ergonomics.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG1 is a schematic diagram of the overall structure of a friction shaft mechanism for increasing or decreasing yarn in a yarn laying machine according to the present application;

[0016] FIG2 is a diagram showing the friction shaft mechanism used in the present application for increasing or decreasing yarn in a yarn laying machine;

[0017] Figure 3 is a schematic diagram of the cutter and prepreg passage;

[0018] In the figure, 1- friction shaft body, 2- cam, 3- first compression spring, 4- retaining edge, 5- friction plate, 6- bearing, 7- key, 8- keyway, 22- carbon fiber cutter;

[0019] 41 - anvil wheel, 42 - second compression spring, 43 - trigger cylinder, 44 - prepreg yarn path. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below with reference to the accompanying drawings.

[0021] The present embodiment is a friction shaft mechanism for increasing or decreasing yarn in a silk laying machine, the mechanism comprising a friction shaft body, a plurality of cams being sleeved on the outer end of the friction shaft body, a group of compression springs being arranged at one end of the friction shaft body, and a load-bearing retaining edge being arranged at the other end; friction plates and cams are sleeved on the friction shaft body in alternating order.

[0022] Furthermore, a bearing is installed inside the cam, and there is no bearing inside the friction plate, but a keyway is provided to cooperate with the key on the friction shaft body.

[0023] Furthermore, a corresponding anvil wheel is provided on the surface of one side of each cam, and the anvil wheel is pre-tightened by a compression spring; a carbon fiber prepreg cutter is arranged on each cam, and the prepreg yarn path passes between the cam and the anvil wheel.

[0024] Furthermore, a trigger cylinder is arranged on the outer side of the cam, and the trigger in the trigger cylinder is clamped into the groove on the cam.

[0025] Furthermore, the friction plate is a double-layer structure with an inner and outer layer, the inner layer is a metal core that cooperates with the key on the friction shaft body, and the outer layer is a friction consumable plate made of non-metallic material.

[0026] As shown in Figures 1 to 3, the outer end of the friction shaft body 1 is sleeved with several sets of cams 2. A first set of compression springs 3 is positioned at one end of the friction shaft body 1, and a load-bearing rib 4 is positioned at the other end. Between the first compression springs 3 and the load-bearing rib 4, friction plates 5 are interspersed on the friction shaft body 1 in the order of cam 2, friction plates 5 (the number can be increased depending on the number of prepregs to be processed). Each cam 2 is sandwiched between two friction plates 5. The cams 2 are internally fitted with bearings 6, allowing them to rotate freely and move along the axis of the friction shaft body 1 when not subjected to friction. The friction plates 5, however, are bearingless and have keyways 8 that mate with keys 7 on the friction shaft body 1. They can only move along the axis of the friction shaft body 1 and cannot rotate freely. When the first compression spring 3 applies pressure to the friction plate 5-cam 2 array from one side of the friction shaft body 1, the compression force is sequentially transmitted along the spring 3's compression direction to the end faces of each friction plate 5 and the side faces of the cam 2, ultimately being absorbed by the load-bearing baffle 4. Consequently, when relative rotation or a tendency for relative rotation occurs between the cam 2 and the friction plate 5, a friction torque is generated between them. Because a key 7 and keyway 8 are located between the friction plate 5 and the friction shaft body 1, this structure ensures constant torque transmission between the cam 2 and the friction shaft body 1. The driving torque that each cam 2 receives from the friction shaft body 1 is capped at the sum of the friction torques generated by the two friction plates 5 on either side.

[0027] The working process of the present invention:

[0028] The friction shaft body 1 is driven to rotate by a motor; on the friction shaft body 1, a row of cams 2 are arranged corresponding to the position of each yarn in the carbon fiber prepreg yarn path; above each cam 2 is arranged a corresponding anvil wheel 41, and the anvil wheel 41 is pre-tightened with a second compression spring 42. As shown in Figure 3, the raw material conveying path to be cut, that is, the prepreg yarn path 44, passes between the cam 2 and the anvil wheel 41; the rotation of the friction shaft drives the rotation of the cam to complete the rotation of the carbon fiber prepreg cutter; according to the action rhythm, the outer wheel of the cam 2 is determined Different radii from various points on the profile to the cam shaft, and a carbon fiber cutter 22 is arranged at the corresponding point of the cam. During the process of the cam 2 rotating one circle, the distance between it and the anvil wheel changes; as the distance changes, the prepreg will be in a clamped, free or cut state; a trigger cylinder 43 is arranged on one side of the cam 2, and when the trigger cylinder 43 drives the trigger 44 to fit into the groove on the cam 2, the cam 2 is in a stationary state, and the combined action of the cylinder and the friction shaft can be used to control the reciprocating of this state, thereby completing the actions of stopping the yarn, feeding the yarn and cutting the yarn.

[0029] The friction shaft mechanism for increasing or decreasing yarn in a yarn laying machine, provided in this application, utilizes a serial structure and non-metallic flat friction plates, replacing a parallel structure and metal arc-surface friction plates. This significantly improves the lifespan, environmental adaptability, and reliability of the friction shaft. The friction torque transmitted by the friction shaft of the present invention ensures that the cam, when performing rolling yarn cutting, uses three times the cutting force of a direct-acting yarn cutting mechanism. Even with this cutting force, the torque safety factor for the cam to cut yarn without slipping still reaches a factor of three or greater. Furthermore, the cutter and the raw material operate synchronously during cutting, without mutual interference, significantly improving reliability during high-speed yarn cutting.

[0030] The torque fluctuation range of the new friction shaft used in this invention is reduced to 7% of the fluctuation range of the original mechanism, completely eliminating the problem of trigger jamming caused by the friction torque peak; after 30,000 yarn cutting and feeding cycles, the friction shaft torque decays by only 6%, extending the life of the friction plate under high-intensity use to more than one quarter. At the same time, after the friction torque of each unit is stabilized, the speed ratio of the motor reducer driving the friction shaft can be reduced, further increasing the speed of yarn cutting by 40-50%. The available yarn cutting force of the present invention is increased to more than three times that of the direct-acting yarn cutting method, which can basically eliminate the influence of cutter wear on reliability. Tests have verified that even in the case of cutter blade curling, thousands of high-speed yarn cutting operations can be completed continuously without failure, greatly improving the reliability of the equipment.

[0031] The connections mentioned in this invention are divided into fixed connections and detachable connections. The fixed connection refers to a non-detachable connection, including but not limited to conventional fixed connection methods such as hem connection, rivet connection, adhesive connection, and welding connection. The detachable connection refers to but not limited to conventional detachable connection methods such as threaded connection, snap connection, pin connection, and hinge connection. When the specific connection method is not clearly specified, it is assumed that at least one connection method can always be found among the existing connection methods to achieve the function. Those skilled in the art can make their own selection according to their needs. For example, a welded connection is selected for a fixed connection, and a hinge connection is selected for a detachable connection.

[0032] The above embodiments are merely illustrative of this patent and do not limit its scope of protection. Those skilled in the art may also make partial changes thereto, and as long as they do not exceed the spirit of this patent, they are within the scope of protection of this patent.

Claims

1. Friction shaft mechanism for increasing or decreasing yarn of filament winding machine, characterized in that, The mechanism includes a friction shaft body, and several groups of cams are sleeved on the outer end of the friction shaft body. A set of compression springs are arranged at one end of the friction shaft body, and a bearing edge is arranged at the other end; friction plates and cams are alternately and spacedly sleeved on the friction shaft body in sequence.

2. The friction shaft mechanism for increasing or decreasing yarns of a filament winding machine according to claim 1, wherein, Bearings are installed inside the cams, and there are no bearings inside the friction plates, and there are key grooves that fit with the keys on the friction shaft body.

3. The friction shaft mechanism for increasing or decreasing yarns of the fiber placement machine according to claim 1, wherein One anvil wheel corresponding to each cam is provided on the surface of one side of each cam, and the anvil wheel is pre-tightened with a compression spring; carbon fiber prepreg cutters are arranged on each cam, and the prepreg yarn path passes through between the cam and the anvil wheel.

4. The friction shaft mechanism for increasing or decreasing yarns of a fiber placement machine according to any one of claims 1 to 3, characterized in that, A trigger cylinder is arranged on the outer side of the cam, and the trigger in the trigger cylinder is snapped into the groove on the cam.

5. The friction shaft mechanism for increasing or decreasing yarns of a fiber placement machine according to claim 4, wherein The friction plate is a double-layer structure inside and outside. The inside is a metal core that is keyed to the friction shaft body, and the outside is a friction consumable sheet made of non-metallic material.

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