A valve worm gear box drilling equipment

Abstract

This utility model discloses a drilling equipment for valve worm gear boxes, relating to the field of drilling processing. It includes a worktable; a control panel located on one side of the worktable; a clamping assembly located at the top of the worktable for fixing and clamping the valve worm gear box; a collection chamber formed on the surface of the worktable and cooperating with the clamping assembly to collect debris generated during processing; hydraulic rods symmetrically arranged in the middle of both sides of the worktable; and a rotating drilling assembly located between the two sets of hydraulic rods for drilling the valve worm gear box. This utility model can simultaneously clamp valve worm gear boxes of different sizes, avoiding workpiece deformation caused by uneven force, reducing the risk of clamping loosening, and improving processing efficiency. During processing, simply rotating the drilling tool to the working position allows for switching between different sized drill bits, effectively ensuring the continuity of the production line and processing efficiency.

Description

Technical Field

[0001] This utility model relates to the field of drilling, specifically to a drilling equipment for valve worm gear boxes. Background Technology

[0002] A valve worm gear box is a mechanical transmission device specifically designed to drive the opening and closing of industrial valves. It amplifies the input torque and converts it into precise rotary motion through the meshing of a worm gear and a worm, thereby controlling the valve's opening and closing angle and speed.

[0003] To ensure that the worm gear, worm shaft, bearings, and other components are fixed and precisely fitted within the valve worm gear box, the box body needs to be drilled to ensure that all components can be connected and fitted.

[0004] For example, the authorized utility model patent with application number 202421082872.2 discloses a drilling and tapping device for processing worm gear housings, including a processing table, a worm gear housing placement rack on the top of the processing table, a placement platform on one side of the processing table, a drilling and tapping mechanism on the top of the placement platform, a collection groove on the top of the processing table, installation grooves on the four sides of the collection groove, an installation hole in the middle of the installation groove, a collection cavity in the middle of the processing table, a switch plate on one side of the collection cavity, a collection box inside the collection cavity, and a stabilizing rod in the middle of the collection box.

[0005] However, in the existing valve worm gear box drilling equipment, the drilling of the valve worm gear box needs to be changed according to the size of the part. When drilling operations of different sizes are required, the drill bit needs to be changed more frequently, which increases the workload of the workers and reduces the production efficiency.

[0006] No effective solutions have yet been proposed to address the problems in the relevant technologies. Utility Model Content

[0007] In view of the problems in the related technologies, this utility model proposes a valve worm gear box drilling and processing equipment to overcome the above-mentioned technical problems existing in the existing related technologies.

[0008] Therefore, the specific technical solution adopted by this utility model is as follows:

[0009] A valve worm gear box drilling machine includes a worktable; a control panel disposed on one side of the worktable; a clamping assembly disposed on the top of the worktable for fixing and clamping the valve worm gear box; a collection chamber disposed on the surface of the worktable and cooperating with the clamping assembly for collecting debris generated during processing; hydraulic rods symmetrically disposed in the middle of both sides of the worktable; and a rotary drilling assembly disposed between the two sets of hydraulic rods for drilling the valve worm gear box.

[0010] Furthermore, in order to clamp the valve worm gear box, the clamping assembly includes a housing set at the top of the workbench. The housing has a hollow structure, and several sliding grooves are opened at the top of the housing. Each of the sliding grooves is equipped with a sliding block. A support frame is set inside the housing and directly below the sliding grooves. A first rotating shaft is set in the middle of the housing. A rotating plate is set on the outside of the first rotating shaft. A first motor is set at the bottom of the first rotating shaft. Several first connecting shafts are set at the bottom of the rotating plate. Rotating bars are set on the outside of each of the several first connecting shafts.

[0011] Furthermore, to achieve clamping operation and prevent displacement during drilling, a clamping plate is provided at the top of the sliding block, and several friction protrusions are provided on one side of the clamping plate. From left to right, a limit plate and a second connecting shaft are sequentially provided at the bottom of the sliding block, with the second connecting shaft cooperating with the rotating bar. A limit post is inserted between the limit plate and the support frame, and a pressure sensor is provided on the side of the friction protrusions away from the clamping plate. The rotating bar has an L-shaped structure and drives the sliding block to reciprocate under the rotation of the rotating plate. The clamping plate has an arc-shaped structure, and the friction protrusions are linearly arranged from left to right on the arc surface of the clamping plate.

[0012] Furthermore, in order to realize the rotation of the drilling cutter and the drilling operation, the rotary drilling assembly includes a circular chuck symmetrically arranged between hydraulic rods. A second motor is provided at the top of the circular chuck, and a second rotating shaft is provided through the bottom of the second motor and the circular chuck. A bearing is provided between the circular chuck and the second rotating shaft, and a rotating cutter head that slides with the circular chuck is provided at the bottom of the second rotating shaft.

[0013] Furthermore, in order to provide electric support for the drilling cutter, a positive electrode power connection slide rail and a negative electrode power connection slide rail are sequentially arranged at the bottom of the circular chuck near the center, and both the positive electrode power connection slide rail and the negative electrode power connection slide rail are provided with grooves.

[0014] Furthermore, to ensure the power source for the rotating drill bit, several third motors are installed through the bottom of the rotating cutter head. A positive and a negative ring are respectively installed at the top of each third motor, and the drill bit is installed at the bottom of the output shaft of the third motor. Positive and negative plates are symmetrically fixedly connected to both sides of the positive and negative rings. A current-receiving strip is installed at the top of each positive and negative plate; a roller is fitted onto the top of each current-receiving strip, and balls that mate with the grooves are installed at both ends of the roller.

[0015] The beneficial effects of this utility model are as follows:

[0016] 1. Synchronous adjustment and multi-point contact of the valve worm gear box ensures even distribution of clamping force, preventing workpiece deformation or displacement caused by single-point force. This also reduces the risk of loosening and enables efficient workpiece transfer, shortening clamping installation time, reducing operator setup time, shortening processing time, and improving overall processing efficiency. Pre-installation of different sized drill bits eliminates the need for machine stoppage during processing. Simply rotating the drill bit to the working position allows for easy switching between different sizes, minimizing downtime caused by frequent drill bit changes and effectively ensuring production line continuity and processing efficiency.

[0017] 2. By using a clamping assembly to synchronously adjust and clamp the valve worm gear box, the clamping force is evenly distributed, effectively preventing workpiece deformation or displacement due to single-point force, while also reducing the risk of clamping loosening. This method significantly shortens the workpiece clamping and installation time, reduces operator time, improves workpiece turnover efficiency, shortens overall processing time, and enhances processing efficiency.

[0018] 3. By rotating the drilling assembly, when drilling operations of different sizes are required for valve worm gear boxes, different specifications of drilling cutters are pre-installed. During processing, simply rotate the drilling cutter to the processing position to achieve switching between different sized drill bits, reducing losses caused by machine downtime, improving continuous production capacity and processing efficiency. At the same time, based on the principle of pantograph, the power source of the drilling cutter is guaranteed, ensuring normal drilling operations can be achieved even after rotation. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a structural schematic diagram of a valve worm gear box drilling equipment according to an embodiment of the present utility model;

[0021] Figure 2 This is a schematic diagram of another angle structure of a valve worm gear box drilling equipment according to an embodiment of the present utility model;

[0022] Figure 3 This is one of the cross-sectional views of a valve worm gear box drilling equipment according to an embodiment of the present utility model;

[0023] Figure 4 yes Figure 3 Enlarged view of a portion at point A;

[0024] Figure 5 This is a partial cross-sectional view of a rotary drilling assembly in a valve worm gear box drilling equipment according to an embodiment of the present utility model;

[0025] Figure 6 This is a bottom-view structural diagram of the clamping component in a valve worm gear box drilling equipment according to an embodiment of the present utility model;

[0026] Figure 7 This is a partial cross-sectional view of a clamping component in a valve worm gear box drilling equipment according to an embodiment of the present utility model.

[0027] In the picture:

[0028] 1. Workbench; 2. Control panel; 3. Clamping assembly; 301. Housing; 302. Sliding groove; 303. Sliding block; 304. Support frame; 305. First rotating shaft; 306. Rotating plate; 307. First motor; 308. First connecting shaft; 309. Rotating bar; 310. Clamping plate; 311. Friction protrusion; 312. Limiting plate; 313. Second connecting shaft; 314. Limiting post; 315. Pressure sensor; 4. Collection 601. Cavity; 602. Hydraulic rod; 603. Rotary drilling assembly; 604. Circular chuck; 605. Second motor; 606. Second rotating shaft; 607. Rotary cutter head; 608. Positive electrode connecting slide rail; 609. Negative electrode connecting slide rail; 6000. Slide groove; 601. Third motor; 610. Positive electrode ring; 611. Negative electrode ring; 612. Drilling cutter; 613. Positive electrode plate; 614. Negative electrode plate; 615. Electric receiving bar; 616. Roller; 617. Ball bearing. Detailed Implementation

[0029] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are usually used to represent similar components.

[0030] According to an embodiment of the present invention, a drilling and machining equipment for valve worm gear boxes is provided.

[0031] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figures 1-7As shown, the valve worm gear box drilling equipment according to an embodiment of the present invention includes a workbench 1; a control panel 2, disposed on one side of the workbench 1; a clamping assembly 3, disposed on the top of the workbench 1, for fixing and clamping the valve worm gear box; a collection chamber 4, opened on the surface of the workbench 1 and cooperating with the clamping assembly 3, for collecting the debris generated during processing; hydraulic rods 5, symmetrically disposed in the middle of both sides of the workbench 1; a rotary drilling assembly 6, disposed between the two sets of hydraulic rods 5, for drilling the valve worm gear box; and a pressure sensor disposed inside the clamping assembly.

[0032] It should be noted that the first motor 307, pressure sensor 315, hydraulic rod 5, second motor 602, positive-pole energized slide rail 605, negative-pole energized slide rail 606, and third motor 608 are electrically connected to the control panel 2. The start command is issued through the human-machine interface (HMI) of the control panel 2. This signal is transmitted from the HMI to the PLC programmable logic controller. After receiving the command, the PLC controls the start, stop, rotation, and power of the above components to achieve precise operation of each component. This is existing technology and will not be elaborated on further here.

[0033] In one embodiment, the clamping assembly 3 includes a housing 301 disposed at the top of the workbench 1. The housing 301 has a hollow structure, and a plurality of sliding grooves 302 are formed at the top of the housing 301. Each of the sliding grooves 302 is provided with a sliding block 303. A support frame 304 is disposed inside the housing 301 and directly below the sliding grooves 302. A first rotating shaft 305 is disposed in the middle of the housing 301. A rotating plate 306 is disposed on the outside of the first rotating shaft 305. A first motor 307 is disposed at the bottom of the first rotating shaft 305. A plurality of first connecting shafts 308 are disposed at the bottom of the rotating plate 306. A rotating bar 309 is disposed on the outside of each of the plurality of first connecting shafts 308. A clamping plate 310 is provided at the top of the sliding block 303, and several friction protrusions 311 are provided on one side of the clamping plate. A limit plate 312 and a second connecting shaft 313 are sequentially provided at the bottom of the sliding block 303 from left to right, and the second connecting shaft 313 is connected to the rotating bar 309. A limit post 314 is inserted between the limit plate 312 and the support frame 304. A pressure sensor 315 is provided on the side of the friction protrusions 311 away from the clamping plate 310. The rotating bar 309 has an L-shaped structure and drives the sliding block 303 to reciprocate under the rotation of the rotating plate 306. The clamping plate 310 has an arc-shaped structure, and the friction protrusions 311 are linearly arranged from left to right on the arc surface of the clamping plate 310 to achieve fixed clamping of the valve worm gear box.

[0034] It should be added that the working principle of the pressure sensor 315 is to detect the change in resistance of the material when it is under pressure and convert it into an electrical signal. This is existing technology and will not be elaborated on here.

[0035] The working principle of the clamping assembly 3 is as follows: When the valve worm gear box is placed on the top of the housing 301, the operator sends a start command to the first motor 307 through the control panel 2. Upon receiving the start command, the output shaft of the first motor 307 drives the rotating plate 306 on the first rotating shaft 305 to rotate, and at the same time drives the first connecting shaft 308 at the bottom of the rotating plate 306 to rotate. At this time, the rotating bar 309 on the outside of the first connecting shaft 308 is also driven to rotate. At this time, the sliding block 303 connected to the rotating bar 309 through the second connecting shaft 313 moves linearly inside the sliding groove 302, and at the same time drives the limiting plate 312 to move synchronously on the limiting post 314. As the sliding block 303 gradually moves inward... When in motion, the clamping plate 310 retracts to clamp the valve worm gear box, and the friction protrusion 311 provides friction and anti-slip function for the valve worm gear box. When the pressure sensor 315 on one side of the friction protrusion 311 detects that the pressure has reached the preset threshold, it sends a stop signal to the control panel 2, thereby controlling the first motor 307 to stop working (the pressure sensor 315 can be MPX5700, HSCARDRRN005MGAA5, etc.). After the drilling operation is completed, the control panel sends a reverse command to the first motor 307, so that the electric rotating plate 306 rotates in the opposite direction, causing the sliding block 303 to move outward in a straight line, ending the clamping of the valve worm gear box.

[0036] In one embodiment, the rotary drilling assembly 6 includes a circular chuck 601 symmetrically arranged between hydraulic rods 5. A second motor 602 is mounted on the top of the circular chuck 601, and a second rotating shaft 603 is mounted on the bottom of the second motor 602, passing through the circular chuck 601. A bearing is provided between the circular chuck 601 and the second rotating shaft 603, and a rotary cutter head 604 that slides with the circular chuck 601 is mounted on the bottom of the second rotating shaft 603. A positive electrode contact slide rail 605 and a negative electrode contact slide rail 606 are sequentially arranged on the bottom of the circular chuck 601 near the center, and both the positive electrode contact slide rail 605 and the negative electrode contact slide rail 606 have grooves 607 formed within them. A plurality of third motors 608 are installed through the bottom end of the rotary cutter head 604. A positive electrode ring 609 and a negative electrode ring 610 are respectively installed at the top of the third motors 608. A drilling cutter 611 is installed at the bottom end of the output shaft of the third motors 608. Positive electrode plates 612 and negative electrode plates 613 are symmetrically fixedly connected to both sides of the positive electrode ring 609 and the negative electrode ring 610. A current receiving strip 614 is installed at the top of both the positive electrode plate 612 and the negative electrode plate 613. A roller 615 is sleeved on the top of the current receiving strip 614, and ball bearings 616 that cooperate with the sliding groove 607 are installed at both ends of the roller 615.

[0037] It should be further explained that the rollers 615 and 616 are made of highly conductive metal materials (such as silver, copper, etc.). During the power transmission process, the positive electrode connecting slide rail 605, negative electrode connecting slide rail 606, slide groove 607, positive electrode ring 609, negative electrode ring 610, positive electrode plate 612, negative electrode plate 613, receiving bar 614, rollers 615 and 616 cooperate with each other to transmit power. The working principle of the positive electrode connecting slide rail 605, negative electrode connecting slide rail 606, positive electrode plate 612, negative electrode plate 613 and receiving bar 614 is the same as the working principle of a pantograph. This is existing technology and will not be elaborated on here.

[0038] In addition, the contact surfaces of the positive electrode contact rail 605, the negative electrode contact rail 606 and the ball bearing 616 can be carbon slide plate structures made of carbon fiber, 150-mesh graphite, 180-mesh electrolytic copper powder and phenolic resin, which give it excellent friction performance and good conductivity when supplying power, ensuring stable current transmission, and also high impact resistance.

[0039] The working principle of the rotary drilling assembly 6 is as follows: First, the operator energizes the positive terminal energized slide rail 605 and the negative terminal energized slide rail 606 through the control panel 2. Then, the current from the positive terminal energized slide rail 605 and the negative terminal energized slide rail 606 is transmitted to the positive terminal plate 612 and the negative terminal plate 613 through the ball bearing 616 and the receiving bar 614. Under the action of the positive terminal ring 609 and the negative terminal ring 610, the power is supplied to the third motor 608, which drives the drilling cutter 611 to perform operations. At this time, the control panel 2 sends a descent command to the hydraulic rod 5, causing the drill bit 611 to gradually press against the drilling work area of ​​the valve worm gear box. When it is necessary to rotate the drill bit 611, the control panel 2 sends an ascending command to the hydraulic rod, raising the rotating drilling assembly 6 to a safe distance. Then, the second motor 602 is started. The output shaft of the second motor 602 drives the second rotating shaft 603 to rotate for a preset time, thereby driving the entire rotating cutter head 604 to rotate, thus enabling the drill bit 611 to rotate directly above the workpiece to be processed. During rotation, the positive ring 609 and negative ring 610 on the third motor 608 drive the positive plate 612, negative plate 613 and current receiving bar 614 to move, causing the ball bearing 616 to move synchronously within the slide groove 607, ensuring that the drill bit 611 can still work normally after rotation.

[0040] To facilitate understanding of the above-mentioned technical solutions of this utility model, the working principle or operation method of this utility model in actual process will be described in detail below.

[0041] In practical application, firstly, the operator places the valve worm gear box to be processed on the top of the outer casing 301. Then, the first motor 307 is started through the control panel 2, causing the sliding block 303 to drive the clamping plate 310 to clamp and fix the valve worm gear box (the working principle of the clamping assembly 3 is as described above). Next, the collection box is placed directly below the collection chamber 4. After the clamping plate 310 fixes the valve worm gear box, the output shaft of the first motor 307 stops outputting. Then, the operator connects the positive and negative terminals of the sliding rail 605 through the control panel 2. When the energized slide rail 606 is energized, the current is transmitted through the ball bearing 616 and the receiving bar 614 to the third motor 608 connected to the positive ring 609 and the negative ring 610, thereby driving the drilling cutter 611 to perform operations (the working principle of the rotary drilling assembly 6 is as described above). The control panel 2 drives the two sets of hydraulic rods 5, which in turn drive the rotary drilling assembly 6 and the drilling cutter 611 to move up and down, so that the drilling cutter 611 gradually approaches the processing area of ​​the valve worm gear box. The debris generated during processing falls into the collection box through the collection chamber 4 for collection and processing.

[0042] When it is necessary to rotate and change the drilling cutter 611, the operator sends a start command to the second motor 602 through the control panel 2. Upon receiving the start command, the output shaft of the second motor 602 drives the second rotating shaft 603 to rotate for a preset duration, thereby rotating the drilling cutter 611 on the rotating cutter disc 604 to the correct position. At this time, the third motor 608 drives the ball bearing 616 to move within the slide groove 607, simultaneously driving the current receiving bar 614, the positive electrode plate 612, and the negative electrode plate 613 to move synchronously, ensuring that the drilling cutter 611, after stopping rotation, can operate normally. The hydraulic rod 5 is controlled to move up and down to perform machining operations on the valve worm gear box.

[0043] After the drilling is completed, the control panel 2 controls the first motor 307 to move the clamping plate 310 in the opposite direction, releasing the clamp on the valve worm gear box. Then, the hydraulic rod 5 lifts the rotating drilling assembly 6 to the top, and then the positive terminal energized slide rail 605 and the negative terminal energized slide rail 606 in the circular chuck 601 are de-energized.

[0044] In summary, by utilizing the above-mentioned technical solution of this utility model, the clamping assembly, through synchronous adjustment of the clamping plate and multi-point contact, ensures uniform distribution of the clamping force, avoiding workpiece deformation or displacement caused by single-point force, reducing the risk of clamping loosening, and enabling efficient workpiece transfer. This shortens clamping installation time, reduces operator installation time, reduces processing time, and improves processing efficiency. Furthermore, by rotating the drill bit assembly and pre-installing drill bits of different sizes, different drill bits can be quickly selected during processing, reducing downtime losses caused by drill bit replacement.

[0045] In this utility model, unless otherwise explicitly specified and limited, the terms "installation", "setting", "connection", "fixing", "screw connection", etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0046] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A valve worm gear box drilling apparatus, characterized by, include: Workbench (1); A control panel (2) is located on one side of the workbench (1); The clamping assembly (3) is located at the top of the workbench (1) and is used to clamp the valve worm gear box. The collection chamber (4) is opened on the surface of the worktable (1) and cooperates with the clamping assembly (3) to collect the debris generated during processing; Hydraulic rods (5) are symmetrically arranged in the middle of both sides of the workbench (1); A rotary drilling assembly (6) is positioned between the two sets of hydraulic rods (5) and is used to drill the valve worm gear box. The rotary drilling assembly (6) includes a circular chuck (601) symmetrically arranged between the hydraulic rods (5). A second motor (602) is provided at the top of the circular chuck (601). A second rotating shaft (603) is provided through the bottom of the second motor (602) and passes through the circular chuck (601). A bearing is provided between the circular chuck (601) and the second rotating shaft (603). A rotary cutter head (604) that slides with the circular chuck (601) is provided at the bottom of the second rotating shaft (603). The bottom end of the circular chuck (601) is provided with a positive electrode contact slide rail (605) and a negative electrode contact slide rail (606) in sequence near the center of the circle, and both the positive electrode contact slide rail (605) and the negative electrode contact slide rail (606) are provided with a groove (607).

2. The valve worm gear box drilling equipment according to claim 1, characterized in that, The clamping assembly (3) includes a housing (301) disposed at the top of the workbench (1). The housing (301) has a hollow structure. Several sliding grooves (302) are opened at the top of the housing (301). Sliding blocks (303) are provided inside the several sliding grooves (302). A support frame (304) is provided inside the outer casing (301) and directly below the sliding groove (302). A first rotating shaft (305) is provided in the middle of the outer casing (301). A rotating plate (306) is provided on the outside of the first rotating shaft (305). A first motor (307) is provided at the bottom end of the first rotating shaft (305). The bottom end of the rotating plate (306) is provided with a plurality of first connecting shafts (308), and the outer side of each plurality of first connecting shafts (308) is provided with a rotating bar (309).

3. The valve worm gear box drilling equipment according to claim 2, characterized in that, The top of the sliding block (303) is provided with a clamping plate (310), and a plurality of friction protrusions (311) are provided on one side of the clamping plate. The bottom of the sliding block (303) is provided with a limiting plate (312) and a second connecting shaft (313) from left to right. The second connecting shaft (313) is connected to the rotating bar (309). A limiting post (314) is inserted between the limiting plate (312) and the support frame (304). Pressure sensors (315) are provided on the side of the plurality of friction bumps (311) away from the clamping plate (310).

4. The valve worm gear box drilling equipment according to claim 2, characterized in that, The rotating bar (309) has an L-shaped structure and drives the sliding block (303) to reciprocate under the rotation of the rotating plate (306).

5. The valve worm gear box drilling equipment according to claim 3, characterized in that, The clamping plate (310) has an arc-shaped structure, and the friction protrusions (311) are arranged linearly from left to right on the arc surface of the clamping plate (310).

6. The valve worm gear box drilling equipment according to claim 1, characterized in that, A plurality of third motors (608) are provided through the bottom end of the rotating cutter head (604). A positive pole ring (609) and a negative pole ring (610) are respectively provided at the top end of the third motor (608). A drilling cutter (611) is provided at the bottom end of the output shaft of the third motor (608).

7. The valve worm gear box drilling equipment according to claim 6, characterized in that, Positive electrode plate (612) and negative electrode plate (613) are symmetrically fixedly connected to both sides of the positive electrode ring (609) and the negative electrode ring (610). A power receiving strip (614) is provided on the top of both the positive electrode plate (612) and the negative electrode plate (613). The top of the receiving bar (614) is fitted with a roller (615), and both ends of the roller (615) are provided with balls (616) that cooperate with the groove (607).

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