Full-automatic six-pole piston floating chuck and workpiece clamping mechanism

Abstract

This invention relates to a fully automatic six-bar piston floating chuck and a workpiece clamping mechanism. The floating chuck is equipped with a hydraulic cylinder mounted on a main shaft. The hydraulic cylinder has a rotary cylinder body and an annular piston conformally to the rotary cylinder body. The annular piston has multiple piston rods evenly spaced. A hollow turntable is located at the front of the hydraulic cylinder. The front ends of each piston rod are flexibly connected to the turntable. Several eccentric grooves are provided on the inner circular surface of the turntable. Ball bearings and thrust springs located circumferentially behind the ball bearings are placed within these eccentric grooves. The depth of the eccentric groove bottom within the ball bearing's range of motion gradually decreases from back to front. The clamping mechanism employs the aforementioned floating chuck and a matching live center. The floating chuck of this invention effectively avoids obstruction to the loading and unloading of robotic arms, effectively avoids obstruction to workpiece end-face grinding, effectively avoids obstruction to workpiece center runout, and effectively avoids scratching the workpiece surface, making it better suited for machining the outer diameter of workpieces such as locomotive axles.

Description

Technical Field

[0001] This invention relates to a fully automatic six-bar piston floating chuck and a workpiece clamping mechanism using such a floating chuck, belonging to the field of mechanical technology. Background Technology

[0002] Most existing grinding machines use chucks for workpiece clamping at the headstock and tailstock. The workpiece is clamped and connected to the worktable, and the machine tool's power rotates the workpiece for machining operations such as cutting and grinding. Existing chucks come in various forms. Based on the number of jaws, they can be divided into two-jaw chucks, three-jaw chucks, four-jaw chucks, six-jaw chucks, and special chucks; based on the power source, they can be divided into manual chucks, pneumatic chucks, hydraulic chucks, electric chucks, and mechanical chucks; and based on their structure, they can be divided into hollow chucks and solid chucks. For example, Chinese patent document CN111673617A discloses a floating jaw chuck for a grinding machine, including a first chuck, a second chuck, a slide groove, a first slider, jaws, a rotating rod, a spring, a first movable block, a first turntable, a fixed shaft, a rotating block, an end face gear, a gear ring, a second turntable, a second movable block, a second slider, a fixed block, a connecting rod, a fixed rod, an extension shaft, a screw, a nut, a sleeve shaft, and a limiting rod. The rotating rod design ensures that when clamping a workpiece, it contacts the workpiece first. During continued clamping, the rotation of the rotating rod pushes the workpiece to move axially. The floating of the workpiece improves the stability of the clamping and avoids workpiece displacement during processing. The second chuck design facilitates support for the inner wall of tubular workpieces, solving the problem of workpiece deformation due to excessive force during clamping and avoiding workpiece movement due to insufficient clamping force. Chinese patent document CN115723044A discloses a floating chuck for a cylindrical grinding machine. It employs a cylinder to drive the pawls and a ratchet wheel, with a one-way needle roller bearing restricting the floating disc's reverse rotation. A positioning shaft is fixed to the floating disc. The ratchet wheel and accumulator drive three pawls to rotate bidirectionally along their respective positioning shafts, with each pawl having an eccentric arc shape. Gaps are left between the floating disc's inner hole and both sides and the mounting base. A separate mechanism drives the three pawls to rotate in opposite directions, while an internal accumulator drives them to rotate in the forward direction. The eccentric arc shape of the pawls allows for expansion and contraction of the pawl opening. The floating disc controls the effective contact between each pawl's claw and the rotating shaft, thus achieving automatic clamping and release of the shaft. This pneumatically driven floating chuck enables automatic clamping and release during the shaft grinding process. During operation, the drive mechanism separates from the chuck, and the fixture has a short footprint, providing the necessary conditions for automating shaft grinding. Chinese patent document CN107225445A discloses a high-precision hydraulic chuck for a CNC precision cylindrical grinding machine, including a chuck body, springs, spring bolts, clamping sliding sleeves, jaws, cylinder top pins, pistons, and cylinder covers. A reciprocating piston is located on one side of the chuck body, and a cylinder cover is located on the outside of the piston. Multiple reciprocating clamping sliding sleeves are movably connected to the inside of the piston via cylinder top pins. Stacked springs and stacked spring bolts for fixing the stacked springs are installed inside the clamping sliding sleeves. This chuck features a unique design, small size, large clamping force, convenient adjustment, good repeatability and reproducibility, fast action response, and a set of asymmetrical arc jaws that leave no indentations on the workpiece, resulting in a long service life.Chinese patent document CN113878495A discloses a floating jaw chuck for a grinding machine, including a base with a mounting groove of a convex shape. The mounting groove contains jaws that are independently adjustable. Universal couplings are movably mounted between the sides of adjacent jaws. By using multiple independently adjustable jaws and a self-aligning mechanism within the jaws, the position and state of the jaws can be independently adjusted according to the shape and eccentricity of the workpiece surface, allowing for better direct clamping of the workpiece and preventing it from deviating from the machining center without the need for additional auxiliary mechanisms. The retractable universal couplings do not restrict the independent adjustment of the position of each jaw, and also allow the angles of the other eccentric chucks to change synchronously when the angle of one eccentric chuck is adjusted, facilitating workpiece loading. These existing technologies each have their own characteristics and are suitable for various adaptive applications. However, certain limitations still exist. In particular, with the continuous improvement of production efficiency in the modern machining industry, more and more customers are demanding high-efficiency end face cylindrical grinding machines. They require automatic loading and unloading with robotic arms on fully automated production lines. At the same time, they also require that an end face cylindrical grinding machine can complete the grinding of both end faces and outer diameter of the workpiece in one setup. The existing technologies mentioned above still need further improvement in terms of how to avoid hindering the loading and unloading of robotic arms, how to avoid hindering the grinding of the workpiece end face, how to avoid hindering the runout of the workpiece center, and how to avoid scratching the workpiece surface, so as to better adapt to the end face cylindrical machining of workpieces such as locomotive axles. Summary of the Invention

[0003] The purpose of this invention is to provide a fully automatic six-bar piston floating chuck and workpiece clamping mechanism that can better adapt to the machining of the outer diameter of workpiece end faces such as locomotive axles.

[0004] The technical solution of this invention is: a fully automatic six-bar piston floating chuck, equipped with a hydraulic cylinder, wherein the hydraulic cylinder is equipped with a rotary cylinder body (hereinafter referred to as cylinder body) and an annular piston (hereinafter referred to as piston) conforming to the rotary cylinder body (the hollow cavity inside the cylinder body). The rotary cylinder body is fixedly mounted on the main shaft. The annular piston is equipped with multiple piston rods. A hollow turntable (with a central through hole) is provided on the front side of the hydraulic cylinder. The front end of each piston rod is flexibly connected to the turntable. Several eccentric grooves are provided on the inner circular surface of the turntable. A ball is provided in the eccentric groove and a thrust spring is located on the circumferential rear side of the ball (the opposite side of the clamping direction, that is, the opposite side of the relative movement direction of the ball in the eccentric groove during the clamping process). The front end of the thrust spring is connected to / presses against the ball (the rear side of the ball). The groove bottom depth (the radial distance from the groove bottom to the inner circular surface of the turntable, or groove depth) within the range of ball movement gradually decreases from back to front (from back to front in the clamping direction).

[0005] The preferred number of piston rods is 6, but other numbers of piston rods can be set according to actual needs.

[0006] Normally, the piston rods can be distributed at equal intervals (equiangular distances) on the same circumference, or other regular distribution methods can be adopted, such as non-equidistant mirror symmetry distribution.

[0007] The number of eccentric grooves is preferably the same as the number of piston rods (e.g., 6), each corresponding to a piston rod.

[0008] The two oil circuit interfaces of the cylinder (the rod-side interface and the rodless interface, which can be referred to as the first interface and the second interface of the cylinder, respectively) are connected to the two oil circuit interfaces of the hydraulic control system (correspondingly, they can be referred to as the first interface and the second interface of the hydraulic control system, respectively) through their respective rotary joints, thereby forming the oil supply and return circuit of the hydraulic oil in the cylinder (the specific form of the circuit depends on the setting of the hydraulic control system).

[0009] Furthermore, the rotary joint is rotatably mounted on the outside of the cylinder body.

[0010] Furthermore, the hydraulic control system is equipped with a check valve (including a check valve assembly) with a self-locking function, and the check valve with the self-locking function can be a hydraulically controlled check valve.

[0011] Preferably, the outer end of the piston rod is provided with a pin perpendicular to the piston rod (perpendicular to the central axis of the piston rod), and the turntable is provided with turntable pin holes corresponding to each pin. The pin is inserted into the turntable pin hole, and a flexible spacer is provided between the two (between the pin and the turntable pin hole), thereby realizing a flexible connection between the front end of the piston rod and the turntable.

[0012] For example, the outer edge of the turntable is provided with U-shaped mounting structures with outward openings corresponding to each piston rod. The turntable pin holes are provided on both sides of the U-shaped mounting structure. The outer end of the piston rod is provided with a piston rod pin hole. The pin passes through the piston rod pin hole of the corresponding piston and is inserted into the turntable pin holes located on both sides of the corresponding U-shaped mounting structure.

[0013] Preferably, the piston rod pin hole (axis of the pin hole) provided on the piston rod (outer end of the piston rod) is perpendicular to the piston rod (axis of the piston rod) and perpendicular to the radial direction passing through the center of the pin hole (a straight line direction that intersects the cylinder central axis / extension line perpendicularly), and the axis (or central axis) of the turntable pin hole on the U-shaped mounting structure overlaps with the axis of the piston rod pin hole on the corresponding piston rod (located on the same straight line).

[0014] Preferably, the pin is axially (in the direction of the central axis of the pin or the pin hole) slidingly fitted with the piston rod pin hole on the corresponding piston rod.

[0015] Preferably, the eccentric groove is a groove of equal width, with the main body of the two side groove walls being mutually parallel planes. Its width is adapted to the size of the ball, and can usually be slightly larger than the diameter of the ball, so as to allow the ball to roll back and forth (circumferentially) in the groove under the constraint of the two side groove walls without swaying left and right (rotary axis).

[0016] Preferably, the groove walls on both sides of the eccentric groove opening are provided with constricted steps (capable of forming a constricted step structure), thereby making the groove opening width smaller than the width of the groove (main body part), and allowing a portion of the balls to protrude from the groove opening but not allowing all the balls to come out (that is, the groove opening width is smaller than the ball diameter), thus allowing the balls to protrude from the groove opening and contact the workpiece.

[0017] Preferably, the ball is an elastic ball (or flexible ball).

[0018] The workpiece clamping mechanism can be used in the headstock and tailstock of machining equipment such as grinding machines. It includes a floating chuck and a center. The floating chuck adopts any of the fully automatic six-bar piston floating chucks disclosed in this invention. The center is a live center that passes through the hollow of the floating chuck.

[0019] The beneficial effects of this invention are as follows: Because the chuck adopts a hollow structure, it can work in conjunction with the center to form a workpiece clamping mechanism, collaboratively clamping the workpiece. The rotary cylinder can be directly mounted on the rotary spindle of the headstock and tailstock, adapting to the workpiece-driving operation mode where the headstock and tailstock alternately drive the workpiece. Since there are no jaws, but rather ball bearing clamping, and the ball bearing material is changed from metal to polyurethane or POM, it features flexible clamping and does not scratch the workpiece. It can also automatically adapt to the shape of the workpiece, avoiding over-positioning. Because of the ball bearings, the workpiece is clamped and self-locking is achieved through the elastic balls rolling on the eccentric circular raceway. The self-locking hydraulic check valve ensures self-locking under relevant conditions. It achieves a fully automatic function; during clamping, there is no need for manual or other auxiliary settings to move the workpiece axially, nor is it necessary to manually adjust the jaws to calibrate the workpiece's center.

[0020] The floating chuck of the present invention can effectively avoid hindering the loading and unloading of the robot arm, effectively avoid hindering the grinding of the end face of the workpiece, effectively avoid hindering the runout of the workpiece center, and effectively avoid scratching the surface of the workpiece, making it better suited for the machining of the outer diameter of the end face of workpieces such as locomotive axles. Attached Figure Description

[0021] Figure 1 This is a front view schematic diagram of the floating chuck of the present invention (XX sectional view, clamping state);

[0022] Figure 2 This is a top view (YY sectional view, in the released state) of the floating chuck of the present invention;

[0023] Figure 3 This is a side view (Z-direction view) of the floating chuck of the present invention;

[0024] Figure 4 This is a schematic diagram of the structure of the floating chuck quick maintenance and adjustment mechanism involved in this invention;

[0025] Figure 5 This is a simplified kinematic diagram of the floating chuck of the present invention;

[0026] Figure 6 This is a schematic diagram of the hydraulic control system of the floating chuck of the present invention;

[0027] Figure 7 This is a schematic diagram of the floating chuck coordinating with the robotic arm for loading and unloading in this invention;

[0028] Figure 8 This is a schematic diagram of the structure of the six-bar piston hollow rotary cylinder of the present invention, wherein the left figure shows the front view of the piston and piston rod, and the right figure shows the side view of the rotary cylinder body and piston rod distribution;

[0029] Figure 9 This is a schematic diagram of the flexible clamping mechanism involved in the present invention;

[0030] Figure 10 This is a schematic diagram of the floating connection mechanism involved in the present invention, wherein the left figure is a front view of the relevant parts and the right figure is a side view;

[0031] Figure 11 This is a layout diagram of the grinding machine involved in the present invention;

[0032] Figure 12 This is a partial enlarged view of the floating connection and flexible clamping involved in this invention, wherein the left image is a front view of the relevant part and the right image is a side view. Detailed Implementation

[0033] I. Components of a Floating Chuck

[0034] See Figures 1-3 The fully automatic six-bar piston floating chuck (hereinafter referred to as floating chuck) of the present invention mainly includes the following parts: A. hollow oil cylinder and rotary joint; B. six-piston rod hollow piston; C. floating connection mechanism; D. flexible clamping mechanism.

[0035] The hollow hydraulic cylinder and rotary joint (Part A) includes: cylinder end cover A1, sealing ring A2, cylinder body A3, sealing ring A4, rotary joint A5, bearing A6, bearing spacer A7, rotary joint A8, sealing ring A9, sealing ring A10, screw A11, screw A12, and screw A13.

[0036] The six-piston rod hollow piston (part B) includes: piston B1, piston rod B2 (6 pieces), nut B3, sealing ring B4 and sealing ring B5.

[0037] The floating connection mechanism (part C) includes: pin C1, rubber spacer C2, and snap ring C3.

[0038] The flexible clamping mechanism (or flexible clamping actuator, part D) includes: ball bearings (especially flexible ball bearings) D1, spring D2, turntable D3, screw D4, and end cap D5.

[0039] In addition, other related components are involved in the work process: workpiece E1 (e.g., locomotive axle), live center E2, headstock spindle E3, and grinding wheel E4.

[0040] Figure 1 and Figure 2 The images show the clamped and released states of the floating chuck. In the released state, the hydraulic cylinder drives the turntable D3 to retract, moving it away from the workpiece E1 and the grinding wheel E4, thus providing space for workpiece end face grinding and robot loading / unloading, avoiding interference / obstruction.

[0041] The cylinder body A3 of the rotary cylinder has a hollow, annular (annular cross-section) structure with a central channel (or hollow, usually cylindrical, conforming to the shape of the center point, allowing the center point to pass through to perform its function) for mounting a live center. The cylinder end cap A1 and various sealing rings can be installed according to conventional cylinder designs. The cylinder body (main body) and end cap areas / interfaces are divided on the entire cylinder body for ease of machining and assembly. The piston B1's shape conforms to the annular inner cavity shape of the cylinder. Six piston rods are evenly distributed on the same circumference, passing through corresponding through holes on the cylinder end cap A1. The right end (located inside the cylinder body) is fixed to the piston via a threaded connection (a fastening nut can be installed), and the left end (located outside the cylinder body) has a piston rod pin hole. An assembly of mounting plates for connecting the pins extends from the outer side of the turntable D3, forming a U-shaped mounting structure together with the turntable (main body). Each mounting plate assembly includes two parallel mounting plates (or mounting ears), located on opposite sides of the corresponding pin's circumference. The mounting plates have corresponding turntable pin holes. The pin C1 passes through the corresponding piston rod pin hole and turntable pin hole, with both ends protruding from the outer ends of the turntable pin holes on the corresponding mounting plates and axially fixed (limited) by a retaining ring C3. A rubber spacer C2 is positioned (filled) between the pin and the turntable pin hole, under a certain pressure. Through the deformation of the rubber spacer, the pin is allowed to move axially and radially relative to the turntable pin hole, thus achieving a flexible connection between the pin and the turntable. A small gap or no gap may be left between the pin and the piston rod pin hole to allow for some axial sliding of the pin relative to the piston rod pin hole. The center of the piston rod pin hole is located on the same circumference (or circle). This circumference (the plane on which it is located) is perpendicular to the central axis (or axis) of the floating chuck / cylinder. The central axis of the piston rod pin hole is located on the tangent of the circle at the center of the piston rod pin hole. The axis (central axis) of the turntable pin hole overlaps with the axis (central axis) of the corresponding piston rod pin hole (which has the same pin) (located on the same straight line) and is perpendicular to the two side planes (two large surfaces) of the mounting plate.

[0042] The inner circle (radial inner surface, or inner cylindrical surface, or inner circular surface) of the turntable D3 has several eccentric grooves (e.g., 6, corresponding to 6 piston rods) forming eccentric circular raceways for the balls. The front and rear (axial sides) walls of these eccentric grooves can be flat, perpendicular to the central axis of the floating chuck / cylinder. The bottom of the groove is an eccentric curved surface, typically a cylindrical shape parallel to the central axis of the floating chuck / cylinder. The groove contains balls D1 and a thrust spring located on one side (circumferential side) of the balls. The groove depth (radial dimension from the bottom of the groove to the inner circle of the turntable) on the ball side (within the ball's range of motion) gradually decreases (from the side closer to the thrust spring to the side farther from the thrust spring), roughly aligning with the rotation direction of the turntable. The disc has a cylindrical surface with an eccentric distance along its central axis. The radius of this cylindrical surface is preferably larger than the radius of the inner circle of the disc. The width of the eccentric groove is similar to (or slightly larger than) the diameter of the ball, allowing the ball to roll within the groove. The groove walls on both sides of the groove opening (the opening of the eccentric groove) have constricted steps (steps used to form the constricted structure), making the groove opening width smaller than the width of the groove (the main body). This allows a portion of the ball to protrude from the groove opening but does not allow all the ball to detach (i.e., the groove opening width is smaller than the ball diameter). Suitable groove bottom shape, groove depth, and constricted steps can be configured to allow the ball to move within the eccentric groove. The size of the portion of the ball protruding from the groove opening is limited by the groove depth at the corresponding location, allowing the ball to engage and disengage (release) the workpiece at different positions (e.g., at the two ends of the ball's range of motion).

[0043] Due to the ease of machining the eccentric groove, the turntable can be divided into two parts: the turntable body (the main part of the turntable) and the end cap D5 (or turntable cover plate). The turntable cover plate is located on the front side of the turntable body and is fixedly connected to the turntable body (e.g., threaded connection / bolt fastening) as an integral part. The main part of the eccentric groove (the eccentric groove structure on the body) is machined on the turntable body. The size of the end cap D5 should at least cover the eccentric groove structure on the turntable body, forming the front groove wall of the eccentric groove. The constricted steps on both sides of the groove opening are respectively set at corresponding positions on the turntable body and the turntable cover plate.

[0044] The number of end caps D5 can be several, each set on the front side of its corresponding eccentric groove; alternatively, a large end cap D5 can be used, covering the front side of each eccentric groove simultaneously. The area of ​​this large end cap (the area of ​​its large surface) can be the same as that of the turntable (the main body of the turntable), so that the inner and outer circular surfaces (radial outer surfaces, or outer cylindrical surfaces, or outer circles) of the end cap are completely aligned with the inner and outer circular surfaces of the main body of the turntable, forming cylindrical surfaces of equal diameter.

[0045] According to actual needs, the fixed connection of each related part can be achieved by welding and threaded connection (e.g., fastening connection of fasteners such as screws, bolts and nuts). The fit method and fit clearance of movable connection can be set according to actual needs (sometimes not provided). The connection and sealing of oil circuit can be achieved by setting sealing rings. The tongue and groove or stepped connection / fitting surface can be provided between the interconnected parts according to actual needs.

[0046] II. Working Principle of Floating Chuck

[0047] The cylinder body A3 is fixed to the headstock (or tailstock) spindle E3 or the headstock (or tailstock) rotary dial with four screws A12. Hydraulic oil (or compressed air can be used instead of hydraulic oil, in which case the cylinder can be considered / equivalently replaced by a pneumatic cylinder) is pumped into the rotary cylinder through the rotary joint A5, pushing the piston B1 to the left. The six piston rods B2 fixed on the piston B1 extend (to the left, depending on...) Figure 1 (In the direction shown) the movement, the six sets of pins C1 fixed on the piston rod B2 synchronously and flexibly drive the turntable D3 to move to the left through their respective rubber spacers C2, and fit into the workpiece E1 (at this time, the six sets of springs D2 in the turntable D3 press out the balls D1, which are pushed back onto the eccentric circular raceway by the workpiece E1), and the extension action is completed.

[0048] Headstock spindle E3 rotates clockwise (according to...) Figure 3 (As shown in the direction), the six piston rods B2 flexibly actuate the turntable D3 and the six balls D1 inside it through the rubber spacer C2. The six balls D1 are clamped between the workpiece E1 and the eccentric circular raceway of the turntable D3 and roll clockwise, clamping the workpiece E1 from six directions. The clamping action is completed.

[0049] During the clamping process, a floating connection is simultaneously implemented. On one hand, the turntable D3 floats using 12 rubber spacers C2: axially, it floats through the elastic deformation of the 12 rubber spacers C2; radially, it floats through the elastic deformation of the 12 rubber spacers C2. On the other hand, the 6 pins C1 can slide on the 6 piston rods B2 respectively, achieving floating.

[0050] The six ball bearings D1 can be made of materials with suitable elasticity, such as polyurethane or POM. They can elastically deform during the clamping of the workpiece E1, achieving flexible clamping.

[0051] During the process of chuck clamping and holding workpiece E1, workpiece E1 has been centered by the two live centers E2. Through the above-mentioned floating connection and flexible clamping, the influence of the floating chuck on the center of workpiece E1 (over-positioning) during the clamping process is avoided.

[0052] III. Six-bar piston layout

[0053] Six sets of piston rods B2, pins C1, balls D1, and springs D2 are evenly distributed within a 360° circumference. In addition, six sets (two in each set) of rubber spacers C2 and other parts are also evenly distributed circumferentially.

[0054] Because the pin C1 needs to be inserted into the hole of the turntable D3 without obstruction during installation, it occupies a certain amount of space. To avoid interference, the pins C1, ball bearings D1, and rubber spacers C2 are arranged at 60° intervals, and the components in the same group are also spaced at a certain distance or angle according to actual needs. Similarly, to avoid interference, the oil passage interfaces of screw A12 and rotary joint A8 can be spaced at 15° intervals.

[0055] According to the standards of the end-face cylindrical grinding machine type series, interference with the grinding wheel must be avoided. Therefore, the radial space of the floating chuck is limited, and because a live center E2 is required, the chuck shape must be hollow. Furthermore, the length of the live center E2 is limited (excessive length would reduce the rigidity of the support and positioning), thus limiting the axial space of the floating chuck. To accommodate numerous mechanisms such as floating connections, flexible clamping, hollow cylinders, rotary joints, six-bar pistons, and eccentric raceways within this limited space, the aforementioned staggered (at certain angles) arrangement is necessary to effectively avoid these interferences.

[0056] IV. Quick Adjustment Mechanism Involving Floating Chuck

[0057] See Figure 4 Since floating chucks are used on automated production lines, they should be able to be quickly adjusted when changing workpieces to meet the functional requirements of the clamping range for fixture changes. The floating chuck structure of this invention perfectly meets these requirements. For example, by disassembling the six sets of screws D4 and end caps D5, the vulnerable parts ball bearings D1 and springs D2 can be quickly replaced; by disassembling the six sets of retaining rings C3 and pins C1, the vulnerable part rubber spacers C2 can be quickly replaced.

[0058] To address changes in the diameter of workpiece E1, the turntable D3 can be quickly replaced by disassembling six sets of retaining rings C3 (the diameter of its hollow hole and the shape of its eccentric circular track are scaled accordingly).

[0059] The motion mode of a five- or six-bar piston floating chuck

[0060] See Figure 5 The floating chuck has 6 sets of compound slider mechanisms, which can realize large axial stroke movement and small radial stroke movement (floating). The floating function is ensured when clamping workpiece E1 by the movement and rotation of turntable D3.

[0061] VI. Hydraulic Control System of Floating Chuck

[0062] See Figure 6The hydraulic control system includes: oil pump F1, pressure reducing valve F2, pressure gauge F3, solenoid directional valve F4, hydraulic check valve F5, and oil cylinder F6.

[0063] Hydraulic control principle: The extension and retraction of the floating chuck's piston rod are achieved by switching via the solenoid directional valve F4. The base support stiffness of the floating chuck is adjusted by regulating the pressure reducing valve F2 (which can be observed by the pressure gauge F3). During grinding, if the cylindrical grinding machine experiences a sudden power outage or insufficient pressure due to a malfunction of the oil pump F1, the hydraulic check valve F5 will lock the oil cylinder F6 to stop its movement, preventing potential safety hazards.

[0064] VII. Floating chuck combined with robotic arm for loading and unloading

[0065] See Figure 7 The components involved in the operation of the floating chuck in conjunction with the robotic arm include: headstock G1, floating chuck G2, tailstock G3, and robotic arm G4.

[0066] The working method of a floating chuck in conjunction with a robotic arm for loading and unloading: With the continuous improvement of production efficiency in the modern machining industry, there is an increasing demand for high-efficiency end-face cylindrical grinding machines, requiring automatic loading and unloading with robotic arms on fully automated production lines. Furthermore, an end-face cylindrical grinding machine can grind both end faces and the outer diameter of a workpiece in a single setup. This creates a need for the corresponding functions of the floating chuck of this invention. Compared to common technologies, the drive clamps at both ends of workpiece E1 can be eliminated; the floating chuck G2 directly clamps both ends of workpiece E1 and drives the machine, without causing scratches to the clamping areas. When the robotic arm G4 is loading or unloading, the floating chuck G2 is in the released position and does not interfere with the robotic arm G4.

[0067] Since the floating chucks of the headstock and tailstock do not hinder the operation of the robot, the robot can use any suitable existing technology to carry out loading and unloading operations according to existing operating methods.

[0068] VIII. Structure and Related Characteristics of Floating Chucks

[0069] 1. Six-rod hollow piston (see...) Figure 8 )

[0070] 1) Compared to standard hydraulic cylinders with only one piston and one piston rod, the hydraulic cylinder of this invention uses a hollow piston with six piston rods (which can be called a six-rod hollow piston). Since it is impossible to guarantee that each piston rod reaches the same speed and synchronization when using six standard hydraulic cylinders to drive six piston rods separately, a synchronization mechanism and a speed regulating mechanism are required. However, by using the six-rod hollow piston of this invention (other numbers of piston rods can also be used depending on actual needs), the synchronization of the six piston rods is fundamentally guaranteed, eliminating the need for a synchronization mechanism and a speed regulating mechanism.

[0071] 2) Compared with the closed (solid) structure of the standard oil cylinder, the oil cylinder end cover A1 and the oil cylinder body A3 of the present invention both adopt an annular structure to form an overall hollow structure. The live center E2 can pass through the middle of the oil cylinder end cover A1, thus ensuring that the live center E2 is centered on the workpiece E1 as required by the cylindrical grinding machine.

[0072] 3) From the perspective of processing technology, in order to ensure the smooth operation of the 6 piston rods B2, 6 through holes for assembling the 6 piston rods B2 can be machined on both the cylinder end cover A1 and the piston B1 at the same time, ensuring the positional accuracy of the through holes relative to the center of the parts.

[0073] 2. Flexible clamping mechanism (see...) Figure 9 and Figure 12 )

[0074] 1) Six ball bearings D1 clamp the workpiece E1 from six directions. The ball bearings are made of polyurethane or POM, which are elastic and have a hardness (Shore 50-80 HA) lower than the workpiece hardness (HRC 40-60), thus preventing scratches. Since the workpiece surface has already been ground, if existing double V-block chucks or triple cam chucks with their metal jaws are used, the jaws will slide against the workpiece during clamping, easily causing scratches.

[0075] 2) The movement mode of ball D1 is rolling, which is beneficial for clamping and protecting the workpiece surface; at the same time, it can automatically adapt to the shape of the workpiece and avoid over-positioning.

[0076] 3) The ball bearings are made of elastic material. After clamping the workpiece, the contact area deforms locally into an arc shape close to the workpiece, resulting in a large contact area and easy clamping of the workpiece. At the same time, the friction generated by the pressure makes it difficult for the jaws and the workpiece to slide relative to each other.

[0077] 4) The oscillating base / foundation of the 6 ball bearings D1 is a turntable D3. During the clamping process, they are linked together and can better adapt to clamp the workpiece E1.

[0078] 5) Because the workpiece processed by the end face cylindrical grinding machine is centered by its two ends, and the runout and dimensional tolerance of the outer cylindrical surface meet the processing requirements of the pre-grinding process (e.g., 0.04mm), the floating clamping action of the floating chuck causes the six flexible balls D1 to elastically deform and clamp the workpiece. During the grinding process, sufficient clamping force is continuously maintained through hydraulic oil, and the configured hydraulic control check valve can realize hydraulic locking to prevent fixture failure in the event of a sudden power failure of the machine tool.

[0079] 3. Floating connection mechanism (see Figure 10 and Figure 12 )

[0080] 1) Components involved: pin C1, rubber bushing C2, snap ring C3, turntable D3, spring D2 and ball bearing D1;

[0081] 2) Extension process: After the workpiece E1 is pressed by the two live centers E2, its center is aligned. When the turntable D3 extends, the ball D1 pressed out by the spring D2 is inserted into the workpiece E1 along the chamfer (2×45°) at the end of the workpiece E1. At this time, the ball D1 floats with the spring D2 and finally sticks to the outer surface of the workpiece E1.

[0082] 3) Clamping process: Turntable D3 rotates clockwise, the contact point between the eccentric raceway and ball D1 continuously shrinks, and ball D1 floats under the action of three external forces (the force exerted by the spring, the eccentric raceway, and the workpiece surface, respectively), finally clamping workpiece E1.

[0083] 4) Actuation process: After clamping, turntable D3 and workpiece E1 are fixed together. The 6 piston rods B2 actuate turntable D3 and workpiece E1 through 12 rubber spacers C2, and float as the rubber spacers C2 elastically deform.

[0084] 5) The floating connection includes two parts:

[0085] i) The piston rod B2 and the turntable D3 are connected by a floating connection via an elastomeric rubber spacer C2. During the extension action, the turntable D3 floats to facilitate the entry of the D1 ball into the workpiece E1 and to act as a buffer when the two come into contact. During the clamping action and subsequent continuous movement of the workpiece E1, this prevents the piston rod B2 from over-positioning the workpiece E1, which would affect the machining accuracy.

[0086] ii) The D1 ball and the turntable D3 are connected by a floating connection via spring D2. During the extension action, the D1 ball rolls in the space formed by the turntable D3 and the end cap D5, eventually clamping the workpiece E1. This floating connection allows the D1 ball to quickly approach the outer surface of the workpiece E1 and adapt to its shape.

[0087] 4. Rotary joint

[0088] A rotary joint is used to connect the oil circuit of the oil cylinder. Based on the outer circle of the cylinder body A3, two bearings A6 support the rotary joints A5 and A8 to make rotary motion. Both ends are sealed by two sealing rings A4. The connected oil pipe does not twist when the main shaft rotates.

[0089] 5. Structures to prevent scratches and to avoid affecting vibration.

[0090] 1) When the robot arm is automatically loading and unloading materials, the turntable D3 can quickly move away from the workpiece to facilitate the loading and unloading of the robot arm and avoid interference and collision accidents; when the robot arm leaves, it can also quickly complete the clamping action, reducing the manual loading and unloading of clamps, reducing labor intensity and improving processing efficiency.

[0091] 2) When changing workpieces, the clamping range of the chuck can be adjusted (e.g., from φ100 to φ150) to adapt to changes in the outer diameter of the workpiece, so as to quickly adjust the fixture and improve processing efficiency.

[0092] 3) Six ball bearings D1 clamp the workpiece. Compared with existing double V-block chucks and triple cam chucks, the floating chuck type makes it easy to adjust the jaws and will not damage the workpiece surface.

[0093] 4) When the ball bearing D1 is clamped, its low hardness and rolling clamping prevent scratching the ground surface of the workpiece. A self-locking mechanism is formed on the eccentric raceway, allowing the workpiece E1 to continue moving even with a sudden drop in hydraulic or pneumatic pressure. Because the rubber spacer C2 has elastic deformation capabilities, it does not affect the workpiece's movement during the movement process (similar to a flexible coupling).

[0094] IX. Clamping mechanism and grinding machine

[0095] See Figure 11 The floating chuck of this invention can be used in conjunction with a live center to form a workpiece clamping mechanism for a machine tool, specifically for the headstock and tailstock of a grinding machine. Grinding machines with this clamping mechanism are suitable for grinding the outer cylindrical end faces of large workpieces such as locomotive axles, and can grind both end faces and the outer cylindrical portion of the workpiece in a single clamping operation.

[0096] The grinding machine consists of: headstock G1, tailstock G3, left grinding wheel head G5, right grinding wheel head G6, left slide G7, and right slide G8. Both the headstock G1 and tailstock G3 are equipped with floating chucks G2 and live centers E2. It can complete the grinding processes of both end faces and outer diameter of a shaft in a single setup.

[0097] This invention can meet the following functional requirements:

[0098] 1) Allows the headstock and tailstock of a CNC end face cylindrical grinding machine to drive the workpiece alternately;

[0099] 2) When the robotic arm is loading or unloading materials, the chuck should be removed from the loading / unloading area to avoid interference;

[0100] 3) When grinding both ends of the workpiece with a grinding wheel, the chuck should be withdrawn from the grinding area to avoid interference and ensure that the outer diameter is small enough;

[0101] 4) The chuck is hollow and has a large enough diameter to allow for the fitting of live centers, making it suitable for heavy workpieces such as axles;

[0102] 5) Flexible ball bearings are used to hold the workpiece, which will not scratch the workpiece surface if the workpiece surface has been ground.

[0103] 6) The chuck is equipped with an effective and reliable floating connection so that the center runout of the workpiece is not affected when driving the workpiece.

[0104] All directional indications (e.g., left, right, etc.) in this specification are only used to explain the relative positional relationship of the relevant components in the corresponding direction or in multiple directions under a specific posture or implementation method, and do not constitute a limitation on the actual use direction. If the specific posture changes, the directional indication will also change accordingly. It is also understood that the interchange of relative positions in at least some directions (e.g., circumferential direction) does not hinder the implementation of the technical solution.

[0105] Unless otherwise specified, the preferred and optional technical means disclosed in this invention can be arbitrarily combined to form several different specific embodiments when one preferred or optional technical means is a further limitation of another technical means.

Claims

1. A fully automatic six-bar piston floating chuck, equipped with a hydraulic cylinder, characterized in that... The hydraulic cylinder comprises a rotary cylinder body and an annular piston conforming to the rotary cylinder body. The rotary cylinder body is fixedly mounted on the main shaft. The annular piston has multiple piston rods, totaling six. A hollow turntable is located at the front of the hydraulic cylinder. The front end of each piston rod is flexibly connected to the turntable. Several eccentric grooves are provided on the inner circumference of the turntable, the number of which corresponds to the number of piston rods. Each eccentric groove contains a ball bearing and a thrust spring located circumferentially behind the ball bearing. The depth of the eccentric groove bottom gradually decreases from back to front within the ball bearing's range of motion. A pin is provided perpendicular to the outer end of each piston rod. The turntable has pin holes corresponding to each pin. The pin is inserted into the pin holes, and a flexible spacer is provided between them. The rubber spacer, acting as the flexible spacer, is positioned between the pin and the pin hole, under a certain pressure, thereby achieving a flexible connection between the front end of the piston rod and the turntable. The outer edge of the turntable is provided with U-shaped mounting structures with outward openings corresponding to each piston rod. The turntable pin holes are located on both sides of the U-shaped mounting structures. The outer end of the piston rod is provided with a piston rod pin hole. The pin passes through the piston rod pin hole of the corresponding piston and is inserted into the turntable pin holes located on both sides of the corresponding U-shaped mounting structure. The pin and the piston rod pin hole on the corresponding piston rod are axially slidingly engaged. The hydraulic control system of the cylinder is provided with a hydraulically controlled check valve with a self-locking function. The turntable extension process is as follows: after the workpiece is clamped by two live centers, its center is aligned. When the turntable extends, the ball pressed by the spring is inserted into the workpiece along the chamfer at the end of the workpiece. At this time, the ball floats with the spring and finally sticks to the outer surface of the workpiece. The workpiece clamping process is as follows: the turntable rotates clockwise, and the contact point between the eccentric circular raceway and the ball continuously shrinks. The ball floats under the action of the forces exerted by the spring, the eccentric circular raceway, and the workpiece surface, and finally clamps the workpiece.

2. The fully automatic six-bar piston floating chuck as described in claim 1, characterized in that... The two oil circuit interfaces of the cylinder are respectively connected to the two oil circuit interfaces of the hydraulic control system through their respective rotary joints. The rotary joints are rotatably installed on the outside of the cylinder body. The hydraulic control system is equipped with a one-way valve with a self-locking function.

3. The fully automatic six-bar piston floating chuck as described in claim 1, characterized in that... Each piston rod is distributed at equal intervals on the same circumference.

4. The fully automatic six-bar piston floating chuck as described in claim 1, characterized in that... The piston rod pin hole on the piston rod is perpendicular to the piston rod and perpendicular to the radial direction passing through the center of the pin hole. The axis of the turntable pin hole on the U-shaped mounting structure is on the same straight line as the axis of the piston rod pin hole on the corresponding piston rod.

5. The fully automatic six-bar piston floating chuck as described in claim 1, characterized in that... The eccentric groove is a groove of equal width, and the main body of the two side groove walls is a plane that is parallel to each other.

6. The fully automatic six-bar piston floating chuck as described in claim 5, characterized in that... The eccentric groove has constricted steps on both sides of the groove wall.

7. The fully automatic six-bar piston floating chuck as described in claim 1, characterized in that... The balls are elastic balls.

8. A workpiece clamping mechanism, including a center, characterized in that... It also includes a floating chuck, wherein the floating chuck is a fully automatic six-bar piston floating chuck as described in any one of claims 1-7, and the center is a live center that passes through the hollow of the floating chuck.

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