A double needle sewing machine for garment production
By introducing an automatic feeding and transferring mechanism into a double-needle sewing machine, combined with slide rail and magnet technology, the problem of automatic feeding difficulties in existing sewing machines has been solved. This enables automatic fabric pushing and stable sewing, improving production efficiency and product quality while protecting the safety of operators.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- HEBEI HUABEI PETROLEUM OCCUPATIONAL PROTECTIVE PRODUCTS CO LTD
- Filing Date
- 2025-07-15
- Publication Date
- 2026-06-05
AI Technical Summary
Currently available automatic sewing machines do not have automatic feeding functions, requiring operators to manually push the fabric, which is time-consuming and laborious, and the speed is uneven, which can easily cause the stitches to be too dense or too sparse, affecting product quality. Furthermore, operating a double-needle sewing machine can easily lead to hand injuries.
A double-needle sewing machine for garment production was designed, comprising a sewing machine body, a placement plate, a displacement mechanism, a feeding mechanism, and a transferring mechanism. Through the cooperation of longitudinal and transverse slide rails, the fabric is automatically pushed during the sewing process. The use of magnets and electromagnets ensures the stability and movement stability of the clamping plate, eliminating the need for manual operation.
It enables automatic pushing of the fabric during the sewing process, ensuring uniform pushing speed, improving product quality, avoiding physical injury to operators, and increasing sewing efficiency.
Smart Images

Figure CN224325518U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of double-needle sewing machine technology, and in particular to a double-needle sewing machine for garment production. Background Technology
[0002] Today, with the continuous advancement of industrial technology, sewing machines are increasingly widely used in garment production. While traditional single-needle sewing machines can meet basic sewing needs, they have limitations in handling certain complex garment structures and improving production efficiency. Especially for garment production requiring double-thread stitching, single-needle sewing machines necessitate frequent thread adjustments, which are not only time-consuming and labor-intensive but may also lead to inconsistent and unreliable stitch quality. Therefore, there is an urgent market demand for efficient and stable double-needle sewing machines. Double-needle sewing machines significantly improve garment production efficiency by simultaneously sewing two threads with two needles on a single machine.
[0003] However, existing automatic sewing machines on the market do not have automatic feeding functions, requiring operators to manually push the fabric, which is time-consuming and laborious, and the speed is uneven, which can easily cause the stitches to be too dense or too sparse, affecting product quality. Furthermore, because double-needle sewing machines have two sewing needles, the operator's hands are more likely to be pricked by the sewing needles during the process of pushing the fabric, causing injury to the operator's body.
[0004] Therefore, it is necessary to provide a double-needle sewing machine for garment production to solve the above-mentioned technical problems. Utility Model Content
[0005] To overcome the above-mentioned defects, this utility model provides a double-needle sewing machine for garment production, which solves the technical problems in the prior art.
[0006] According to one aspect, at least one embodiment of the present invention provides a double-needle sewing machine for garment production, comprising: a sewing machine body and a plurality of placement plates for placing fabric, wherein a displacement mechanism is installed on the sewing machine body to move the placement plates, and a feeding mechanism and a transferring mechanism are provided on one side of the displacement mechanism to move the placement plates for loading and unloading fabric.
[0007] The top of the placement plate is provided with a sewing hole, and the two ends of the top of the placement plate are respectively provided with a first clamping plate group and a second clamping plate group. The first clamping plate group and the second clamping plate group have the same structure. The first clamping plate group includes an upper support plate and a lower support plate. The sides of the upper support plate and the lower support plate are respectively rotatably connected to one end of a first rotating shaft and a second rotating shaft. The other ends of the first rotating shaft and the second rotating shaft are respectively fixedly connected to the two sides of the clamping plate.
[0008] The displacement mechanism includes a displacement frame, the top of which is movably connected to the bottom of the placement plate. Both ends of the bottom of the displacement frame are connected to longitudinal slide rails via sliders. The bottoms of the two longitudinal slide rails are installed at both ends of the top of the moving plate. The bottom of the moving plate is connected to a transverse slide rail via a slider. The bottom of the transverse slide rail is connected to the top of a slide rail support seat placed on the ground via a bracket.
[0009] Preferably, the feeding mechanism includes a rotating plate, the top of which is provided with multiple mounting frames, the top of which is movably connected to the bottom of the placement plate, the bottom of which is connected to the drive end of a rotary motor, and the rotary motor is mounted on the top of a rotating support base placed on the ground.
[0010] Preferably, the bottom of the rotating plate is provided with a limiting ring, the limiting ring is rotatably connected to a limiting groove, and the limiting groove is provided at the top of the rotating support.
[0011] Preferably, the material transfer mechanism includes a material transfer plate, with multiple first electromagnets and multiple second electromagnets respectively installed at both ends of the bottom of the material transfer plate. The top of the material transfer plate is connected to the telescopic end of the lifting cylinder, the fixing plate of the lifting cylinder is connected to the bottom of the material transfer rotating plate, the material transfer rotating plate is connected to the drive end of the material transfer motor, and the bottom of the material transfer motor is connected to the top of the material transfer support base through an L-shaped material transfer connecting frame.
[0012] Preferably, there are two lifting cylinders, which are symmetrically arranged on the top of the transfer plate.
[0013] Preferably, the clamping plate is made of iron, and the top of the placement plate is provided with a magnet groove, and a magnet is installed inside the magnet groove.
[0014] Preferably, the sides of the upper support plate and the lower support plate are respectively connected to the two ends of the upper baffle, and an upper magnet is installed on the side of the upper baffle.
[0015] Preferably, the bottom of the placement plate is provided with a rectangular connecting ring, the top of the displacement frame is provided with a displacement groove that mates with the connecting ring, and the top of the mounting frame is provided with a mounting groove that mates with the connecting ring.
[0016] Preferably, the bottom of the connecting ring is provided with multiple fixing grooves, the bottom of the displacement groove is equipped with multiple displacement fixing shafts that cooperate with the fixing grooves, and the bottom of the mounting groove is equipped with multiple mounting fixing shafts that cooperate with the fixing grooves.
[0017] Preferably, the top of the clamping plate is provided with a rotating ring, and the rotating ring is U-shaped.
[0018] Compared with related technologies, the double-needle sewing machine for garment production provided by this utility model has the following beneficial effects:
[0019] In the sewing process, the longitudinal and transverse slide rails work together to allow the placement plate to move in a plane within the sewing area, thereby driving the fabric above it to move synchronously. This enables the fabric to be automatically pushed during the sewing process, effectively controlling the pushing speed and ensuring uniform speed. This guarantees proper stitches, improves product quality, and eliminates the need for manual operation during fabric pushing, thus avoiding injury to the operator.
[0020] This utility model, by setting a transfer motor, can drive the rotation of the transfer plate, and by setting a lifting cylinder, the height of the transfer plate can be adjusted. Furthermore, by setting a double lifting cylinder, the top of the transfer plate is evenly stressed, thus improving the stability of the transfer plate's up and down movement.
[0021] This invention improves the stability of the clamping plate when it is placed on the placement plate by setting a magnet. The upper magnet also limits the clamping plate when it is in the vertical direction, thus improving the stability of the clamping plate when it is placed vertically. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of this utility model, the accompanying drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are merely some exemplary embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the content of the exemplary embodiments of this utility model and these drawings without any creative effort.
[0023] Figure 1 A schematic diagram of a preferred embodiment of a double-needle sewing machine for garment production provided by this utility model;
[0024] Figure 2 for Figure 1 The diagram shown is a structural schematic of the feeding mechanism;
[0025] Figure 3 for Figure 1 The diagram shown is a schematic representation of the structure of a rotary electric motor.
[0026] Figure 4 for Figure 1 The diagram shows the structure of the limiting groove.
[0027] Figure 5 for Figure 1 The diagram shows the structure of the mounting frame.
[0028] Figure 6 for Figure 1 The diagram shows the structure of the placement plate.
[0029] Figure 7 for Figure 1 The diagram shows the structure of the placement plate from a lower view.
[0030] Figure 8 for Figure 1 The diagram shows the structure of the material transfer mechanism.
[0031] Figure 9 for Figure 1 The diagram shown is a structural schematic of the material transfer mechanism from a bottom view.
[0032] Figure 10 for Figure 1 The diagram shows the structure of the displacement mechanism.
[0033] Labels in the diagram: 1. Sewing machine body; 2. Feeding mechanism; 3. Transfer mechanism; 4. Displacement mechanism; 5. Placement plate; 6. First clamping plate assembly; 7. Second clamping plate assembly; 8. Sewing hole; 9. Upper support plate; 10. Lower support plate; 11. First rotating shaft; 12. Clamping plate; 13. Rotating ring; 14. Magnet slot; 15. Magnet; 16. Baffle; 17. Connecting ring; 18. Fixing slot; 201. Rotating plate; 202. Mounting frame; 203. Limiting ring; 204. Support base; 205. Rotary motor 206. Limiting groove; 207. Mounting groove; 208. Mounting fixing shaft; 301. Transfer plate; 302. Lifting cylinder; 303. Transfer rotating plate; 304. Transfer motor; 305. Transfer connecting frame; 306. Transfer support base; 307. First electromagnet; 308. Second electromagnet; 401. Displacement frame; 402. Displacement groove; 403. Displacement fixing shaft; 404. Longitudinal slide rail; 405. Moving plate; 406. Transverse slide rail; 407. Bracket; 408. Slide rail support base. Detailed Implementation
[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit its scope.
[0035] To keep the drawings concise, only the parts relevant to the utility model are shown schematically in each drawing; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of the components with the same structure or function is schematically shown, or only one is labeled. In this document, "a" not only means "only one," but can also mean "more than one," and "several" includes "two" and "more than two."
[0036] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0037] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0038] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.
[0039] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0040] refer to Figures 1 to 10 The present invention provides a double-needle sewing machine for garment production, comprising: a sewing machine body 1 and a plurality of placement plates 5 for placing fabric. A displacement mechanism 4 is installed on the sewing machine body 1 to move the placement plates 5. A feeding mechanism 2 and a transferring mechanism 3 are provided on one side of the displacement mechanism 4 to move the placement plates 5.
[0041] The top of the placement plate 5 is provided with a sewing hole 8. The two ends of the top of the placement plate 5 are respectively provided with a first clamping plate group 6 and a second clamping plate group 7. The first clamping plate group 6 and the second clamping plate group 7 have the same structure. The first clamping plate group 6 includes an upper support plate 9 and a lower support plate 10. The sides of the upper support plate 9 and the lower support plate 10 are respectively rotatably connected to one end of a first rotating shaft 11 and a second rotating shaft. The other ends of the first rotating shaft 11 and the second rotating shaft are respectively fixedly connected to the two sides of the clamping plate 12.
[0042] The displacement mechanism 4 includes a displacement frame 401, the top of which is movably connected to the bottom of the placement plate 5. Both ends of the bottom of the displacement frame 401 are connected to longitudinal slide rails 404 via sliders. The bottoms of the two longitudinal slide rails 404 are mounted on the top ends of the moving plate 405. The bottom of the moving plate 405 is connected to a transverse slide rail 406 via sliders. The bottom of the transverse slide rail 406 is connected to the top of a slide rail support 408 placed on the ground via a bracket 407.
[0043] It should be noted that the sewing machine body 1 is a double-needle sewing machine in the prior art, and the longitudinal slide rail 404 and the transverse slide rail 406 adopt electric slide rails in the prior art.
[0044] The fabric to be sewn is manually placed on the placement plate 5, with the stitching area positioned above the sewing hole 8. The two ends of the fabric are secured under the clamping plates 12 of the first and second clamping plate groups 6 and 7, respectively, by the rotatable first clamping plate group 6 and second clamping plate group 7. The clamping plates 12 firmly hold the fabric to the placement plate 5. Then, the feeding mechanism 2 moves the placement plate 5, now secured with the fabric, below the transfer mechanism 3. The transfer mechanism 3 then moves the placement plate 5, now secured with the fabric, onto the frame. Under the action of the longitudinal slide rail 404, the placement plate 5 is moved to the sewing area of the sewing machine body 1. During the sewing process, under the combined action of the longitudinal slide rail 404 and the transverse slide rail 406, the placement plate 5 can move in a plane in the sewing area, thereby driving the fabric above it to move synchronously, realizing automatic pushing of the fabric during the sewing process. It can effectively control the pushing speed, make the pushing speed uniform, ensure proper stitches, improve product quality, and eliminate the need for personnel operation during the pushing of the fabric, thus avoiding injury to the operator.
[0045] After sewing is completed, the four placement plates 5 are moved to the bottom of the transfer mechanism 3 via the displacement mechanism, and exchanged with the next placement plate 5 that needs to be sewn via the transfer mechanism 3. The sewn placement plate 5 is then rotated to one side via the feeding mechanism 2, and the material is unloaded manually. Through the above operations, the automatic feeding, sewing, and unloading of the fabric are realized, which effectively improves the sewing efficiency.
[0046] In the embodiments of this utility model, reference is made to Figure 2 As shown, the feeding mechanism 2 includes a rotating plate 201. The top of the rotating plate 201 is provided with multiple mounting frames 202. The top of the mounting frames 202 is movably connected to the bottom of the placement plate 5. The bottom of the rotating plate 201 is connected to the drive end of the rotary motor 205. The rotary motor 205 is mounted on the top of the rotating support base 204 placed on the ground.
[0047] In the embodiments of this utility model, reference is made to Figure 3 , Figure 4 As shown, the bottom of the rotating plate 201 is provided with a limiting ring 203, the limiting ring 203 is rotatably connected to the limiting groove 206, and the limiting groove 206 is provided on the top of the rotating support 204.
[0048] It should be noted that by setting the drive of the rotary motor 205, the rotating plate 201 can be rotated, and the mounting frame 202 placed on it can be rotated synchronously to realize the loading and unloading of the placement plate 5. By setting the limit ring 203, the stability of the rotating plate 201 during rotation can be improved through the limit guide of the limit groove 206.
[0049] In the embodiments of this utility model, reference is made to Figure 8 As shown, the material transfer mechanism 3 includes a material transfer plate 301. Multiple first electromagnets 307 and multiple second electromagnets 308 are respectively installed at both ends of the bottom of the material transfer plate 301. The top of the material transfer plate 301 is connected to the telescopic end of the lifting cylinder 302. The fixing plate of the lifting cylinder 302 is connected to the bottom of the material transfer rotating plate 303. The material transfer rotating plate 303 is connected to the driving end of the material transfer motor 304. The bottom of the material transfer motor 304 is connected to the top of the material transfer support 306 through an L-shaped material transfer connecting frame 305.
[0050] In the embodiments of this utility model, reference is made to Figure 8 As shown, there are two lifting cylinders 302, which are symmetrically arranged on the top of the transfer plate 301.
[0051] It should be noted that by setting the transfer motor 304, the transfer plate 301 can be rotated by the drive of the transfer motor 304, and the height of the transfer plate 301 can be adjusted by setting the lifting cylinder 302. Furthermore, by setting the double lifting cylinder 302, the top of the transfer plate 301 is evenly stressed, thereby improving the stability of the transfer plate 301 in moving up and down.
[0052] In the embodiments of this utility model, reference is made to Figure 6 As shown, the clamping plate 12 is made of iron, and the top of the placement plate 5 is provided with a magnet groove 14, and a magnet 15 is installed inside the magnet groove 14.
[0053] In the embodiments of this utility model, reference is made to Figure 6 As shown, the sides of the upper support plate 9 and the lower support plate 10 are respectively connected to the two ends of the upper baffle 16, and the upper baffle 16 is equipped with an upper magnet 15.
[0054] It should be noted that by setting up the magnet 15, the stability of the clamping plate 12 when it is placed on the placement plate 5 can be improved by the magnetic attraction of the magnet 15. Also, by setting up the magnet 15, the clamping plate 12 can be limited when it is in the vertical direction, thus improving the stability of the clamping plate 12 when it is placed vertically.
[0055] In the embodiments of this utility model, reference is made to Figure 7 As shown, the bottom of the placement plate 5 is provided with a rectangular connecting ring 17, the top of the displacement frame 401 is provided with a displacement groove 402 that cooperates with the connecting ring 17, and the top of the mounting frame 202 is provided with a mounting groove 207 that cooperates with the connecting ring 17.
[0056] In the embodiments of this utility model, reference is made to Figure 6 , Figure 10 As shown, the bottom of the connecting ring 17 is provided with a plurality of fixing grooves 18, the bottom of the displacement groove 402 is provided with a plurality of displacement fixing shafts 403 that cooperate with the fixing grooves 18, and the bottom of the mounting groove 207 is provided with a plurality of mounting fixing shafts 208 that cooperate with the fixing grooves 18.
[0057] It should be noted that by setting the connecting ring 17, it can be connected to the displacement groove 402 or the mounting groove 207, thereby improving the stability of the connection between the placement plate 5 and the displacement frame 401 or the mounting frame 202.
[0058] In the embodiments of this utility model, reference is made to Figure 6 As shown, the top of the clamping plate 12 is provided with a rotating ring 13, and the rotating ring 13 is U-shaped.
[0059] It should be noted that by setting the U-shaped rotating ring 13, it is easy to rotate the clamping plate 12 by holding the rotating ring 13.
[0060] The working principle of the double-needle sewing machine for garment production provided by this utility model is as follows:
[0061] The fabric to be sewn is manually placed on the placement plate 5, with the stitching area positioned above the sewing hole 8. The two ends of the fabric are secured under the clamping plates 12 of the first and second clamping plate groups 6 and 7, respectively, by the rotatable first clamping plate group 6 and second clamping plate group 7. The clamping plates 12 firmly hold the fabric to the placement plate 5. Then, the feeding mechanism 2 moves the placement plate 5, now secured with the fabric, below the transfer mechanism 3. The transfer mechanism 3 then moves the placement plate 5, now secured with the fabric, onto the frame. Under the action of the longitudinal slide rail 404, the placement plate 5 is moved to the sewing area of the sewing machine body 1. During the sewing process, under the combined action of the longitudinal slide rail 404 and the transverse slide rail 406, the placement plate 5 can move in a plane in the sewing area, thereby driving the fabric above it to move synchronously, realizing automatic pushing of the fabric during the sewing process. It can effectively control the pushing speed, make the pushing speed uniform, ensure proper stitches, improve product quality, and eliminate the need for personnel operation during the pushing of the fabric, thus avoiding injury to the operator.
[0062] It should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.
Claims
1. A double-needle sewing machine for garment production, characterized in that, include: The sewing machine body (1) and multiple placement plates (5) for placing fabric are provided. The sewing machine body (1) is equipped with a displacement mechanism (4) that can move the placement plates (5). The displacement mechanism (4) is provided with a feeding mechanism (2) that can move the placement plates (5) for loading and unloading, and a material transfer mechanism (3) that can move the placement plates (5) for moving. The top of the placement plate (5) is provided with a sewing hole (8). The two ends of the top of the placement plate (5) are respectively provided with a first clamping plate group (6) and a second clamping plate group (7). The structure of the first clamping plate group (6) and the second clamping plate group (7) is the same. The first clamping plate group (6) includes an upper support plate (9) and a lower support plate (10). The sides of the upper support plate (9) and the lower support plate (10) are respectively rotatably connected to one end of the first rotating shaft (11) and the second rotating shaft. The other ends of the first rotating shaft (11) and the second rotating shaft are respectively fixedly connected to the two sides of the clamping plate (12).
2. A double-needle sewing machine for garment production according to claim 1, characterized in that, The displacement mechanism (4) includes a displacement frame (401), the top of which is movably connected to the bottom of the placement plate (5). Both ends of the bottom of the displacement frame (401) are connected to the longitudinal slide rails (404) via sliders. The bottoms of the two longitudinal slide rails (404) are installed at both ends of the top of the moving plate (405). The bottom of the moving plate (405) is connected to the transverse slide rails (406) via sliders. The bottom of the transverse slide rails (406) is connected to the top of the slide rail support seat (408) placed on the ground via a bracket (407).
3. A double-needle sewing machine for garment production according to claim 2, characterized in that, The feeding mechanism (2) includes a rotating plate (201), the top of which is provided with multiple mounting frames (202). The top of the mounting frames (202) is movably connected to the bottom of the placement plate (5). The bottom of the rotating plate (201) is connected to the drive end of a rotary motor (205), which is mounted on the top of a rotating support base (204) placed on the ground.
4. A double-needle sewing machine for garment production according to claim 3, characterized in that, The bottom of the rotating plate (201) is provided with a limiting ring (203), which is rotatably connected to a limiting groove (206), which is located on the top of the rotating support (204).
5. A double-needle sewing machine for garment production according to claim 1, characterized in that, The material transfer mechanism (3) includes a material transfer plate (301). Multiple first electromagnets (307) and multiple second electromagnets (308) are respectively installed at both ends of the bottom of the material transfer plate (301). The top of the material transfer plate (301) is connected to the telescopic end of the lifting cylinder (302). The fixing plate of the lifting cylinder (302) is connected to the bottom of the material transfer rotating plate (303). The material transfer rotating plate (303) is connected to the driving end of the material transfer motor (304). The bottom of the material transfer motor (304) is connected to the top of the material transfer support base (306) through an L-shaped material transfer connecting frame (305).
6. A double-needle sewing machine for garment production according to claim 5, characterized in that, The number of lifting cylinders (302) is two, and the two lifting cylinders (302) are symmetrically arranged on the top of the transfer plate (301).
7. A double-needle sewing machine for garment production according to claim 3, characterized in that, The clamping plate (12) is made of iron, and the top of the placement plate (5) is provided with a magnet groove (14), and a magnet (15) is installed inside the magnet groove (14).
8. A double-needle sewing machine for garment production according to claim 7, characterized in that, The sides of the upper support plate (9) and the lower support plate (10) are respectively connected to the two ends of the upper baffle (16), and the upper baffle (16) is equipped with an upper magnet (15).
9. A double-needle sewing machine for garment production according to claim 8, characterized in that, The bottom of the placement plate (5) is provided with a rectangular connecting ring (17), the top of the displacement frame (401) is provided with a displacement groove (402) that cooperates with the connecting ring (17), and the top of the mounting frame (202) is provided with a mounting groove (207) that cooperates with the connecting ring (17).
10. A double-needle sewing machine for garment production according to claim 9, characterized in that, The bottom of the connecting ring (17) is provided with multiple fixing grooves (18), and the bottom of the displacement groove (402) is provided with multiple displacement fixing shafts (403) that cooperate with the fixing grooves (18). The bottom of the mounting groove (207) is provided with multiple mounting fixing shafts (208) that cooperate with the fixing grooves (18).