Screw head with combined gripping and rotation mechanism

Abstract

Screw head (1), in particular for a robot, comprising a screw head body (2) on which at least two pivotably mounted screw jaws (3) are arranged, which can selectively assume an open or a closed position for gripping and screwing screw caps (4), such that in the closed position the screw cap (4) is gripped and can be screwed and in the open position the screw cap (4) is released, characterized by a combined gripping and rotational mechanism with limitable torque and freewheel, consisting of an actuator (5) mounted axially movable centrally in the screw head (1) and a gearbox (6) cooperating with the actuator (5), which is designed to convert a movement of the actuator (5) triggered by pressing the actuator (5) against the screw cap to be gripped into a closing movement of the at least two screw jaws (3),to grip the screw cap (4) and from a steep-pitch screw drive (8) with freewheel (7) and slip clutch (9), which is designed to convert a movement of the screw head triggered by pressing the screw head in the closed position of the screw jaws with gripped screw cap against a screw container into a rotational movement of the screw head base body, in order to screw the screw cap (4) to a screw container.

Description

[0001] The invention relates to a screw head for a closure device, in particular robot-guided, for screw caps, comprising a screw head base body on which at least two pivotably mounted screw jaws are arranged, which can selectively assume an open or closed position for gripping and screwing screw caps, such that in the closed position of the screw jaws the screw cap is gripped by the screw head and a screwing torque is transmitted, and in the open position of the screw jaws the screw cap is released, and comprising a steep-pitch screw drive with torque limitation and freewheel, which is designed to convert a linear movement of the screw head, triggered by pressing the screw head in the closed position of the screw jaws with a gripped screw cap against a screw container, into a rotational movement of the screw head base body.to screw on the screw cap.

[0002] A wide variety of screw heads with jaws and gripping functions are known from industry. All such screw heads have in common that they require external drive technology and a corresponding energy supply for controlling the jaws and for rotation during screwing. This is associated with increased resource and installation space consumption, as well as mechatronic integration effort. Particularly in robots, the screw head's interference contour and mass are increased by the necessary supply of energy, drive, and control technology, thus limiting its range of application.

[0003] The object of the invention is to construct a screw head, particularly suitable as a robot end effector, with autonomous gripping and rotational mechanics, which operates without an external energy supply and thus avoids the aforementioned disadvantages.

[0004] The object of the invention is achieved by a screw head, in particular for a robot, comprising a screw head base body on which at least two mounted screw jaws are arranged, which can selectively assume an open or closed position for gripping and screwing screw caps, such that in the closed position of the screw jaws the screw cap is gripped by the screw head and a screwing torque is transmitted, and in the open position of the screw jaws the screw cap is released, and comprising an actuating element movably mounted on the screw head base body and a gear mechanism cooperating with the actuating element, which is designed to convert a movement of the actuating element triggered by pressing the actuating element against the screw cap to be gripped into a closing movement of the at least two screw jaws in order to grip the screw cap.and comprising a steep-pitch screw drive with torque limitation and freewheel, designed to convert a linear movement of the screw head, triggered by pressing the screw head in the closed position of the screw jaws with the screw cap gripped against a screw container, into a rotational movement of the screw head base body in order to screw the screw cap on.

[0005] The independently pivotable screw jaws can be actuated simultaneously or sequentially. This allows for synchronous or asynchronous gripping movements.

[0006] The actuator for controlling the screw jaws can, for example, be designed without a motorized actuation of the screw jaws, wherein the actuator is designed to transmit a force generated by pressure to the screw jaws for their actuation.

[0007] The gearbox may have a locking mechanism or be designed as a locking mechanism.

[0008] The actuator can, for example, have a cone-shaped contour which, during linear movement, generates a linear change in radius relative to a stationary body. The conically contoured actuator can be designed such that a linear movement resulting from a counter-pressure force exerted by the screw cap over a defined linear path "X" causes a corresponding increase in radius.

[0009] The actuator can, for example, have an axially adjustable, cone-shaped contour which, for a given path "X", generates a defined change in radius relative to a stationary body. The adjustability can be designed such that the increase in radius causes a corresponding deflection of the screw jaws with respect to a defined path.

[0010] The gearbox can have a locking mechanism for blocking the return movement of the screw jaws, at least from the closed to the open position, such that the screw jaws are autonomously locked in this state while clamping a screw closure, and a further locking mechanism for blocking the rotational movement of the steep screw drive, at least from the open to the closed position of the screw jaws, such that the steep screw drive is autonomously locked in its position.

[0011] The two locking mechanisms can, for example, be designed as part of the gearbox or act on the gearbox from the outside.

[0012] The gearbox may have a release mechanism for unlocking the locked screw jaws and the steep screw drive, such that the screw jaws can be moved from their closed position to their open position in order to release the screw closure, and may have a further release mechanism by which the steep screw drive can be moved from its blocked position to its movable position in order to exert a torque on the screw closure when a pressure force is applied.

[0013] The two unlocking mechanisms can, for example, be designed as part of the gearbox or act on the gearbox from the outside.

[0014] The gearbox can have a cam guide and a cam follower guided in the cam guide, the cam guide containing two different, alternating types of track sections. The first track section can be configured such that the movement of the screw jaws from the closed to the open position is locked and the movement of the helix screw is released when the cam follower is in this track section. The second track section can be configured such that the movement of the screw jaws from the closed to the open position is released and the helix screw is locked when the cam follower is in this track section.

[0015] The cam follower can be moved from the first to the second track section. Additional track sections or guides can act on the cam follower to achieve this. Together, the track sections and cam follower guides can form the gear mechanism to function as a locking device.

[0016] The high-helix screw drive can be designed such that, for example, the high-helix nut is connected to the robot mount of the screw head via a freewheel, and the high-helix spindle is connected to the screw head body by means of an adjustable torque limiting device. The high-helix screw drive can be locked by the gearbox when the screw jaws are in the open position and freely movable when the screw jaws are in the closed position. This prevents the simultaneous generation of torque on the screw cap when gripping it—that is, when changing from the open to the closed position by applying an axially acting pressure force—which would otherwise require a torque support for the screw cap being gripped, for example, in the form of a clamp.A rotation superimposed on the radial gripping movement of the screw jaws would lead to mechanical damage to the stationary screw cap. Therefore, the gripping action of the screw jaws must consist solely of radially acting movement components. This is particularly true when the high-helix nut is positioned at the lower end of the high-helix spindle. In this state, no compressive force is converted into rotation, and the gripping movement of the screw jaws is purely radial. The freewheel allows the high-helix spindle to be made shorter than without it, because without the freewheel, the number of rotations of the screw cap required for tightening, plus at least one additional screw head rotation for safety (in case the screw thread does not engage immediately), would have to be accommodated on the screw spindle.With a freewheel, the spindle can be made shorter, as the robot can easily perform a kind of pumping motion with several strokes, similar to accelerating a spinning top, to screw on a screw cap.

[0017] Each screw jaw can be pivotally mounted on the screw head body in a clamping direction that grips the screw cap and can have several sections. The first section can be in contact with the screw cap for gripping and tightening. The second section, located between the first and third sections, can be designed as a pivot bearing to translate the change in radius during the linear movement of the actuator onto the screw jaw into a pivoting movement at a specific ratio. The third section can be in contact with the actuator and controlled by it, translating the change in radius during the linear movement of the actuator into a pivoting movement of the screw jaw to perform the functions of clamping and tightening a screw cap.

[0018] In the following, for example, the actuator can also be referred to as a plunger, the T-nut as a switching star, the track section types as short or long grooves in a guide hub, the guides as Hirth teeth on the switching star and the control hub, and the adjustable torque limiting device as a slip clutch, without this being to be interpreted as a restriction of the general inventive idea.

[0019] The solution according to the invention can be described as follows: A screw head attached to a robot arm is proposed to solve the problem; this screw head can, for example, contain three screw jaws. The screw head can further include a plunger located concentrically in the axis of rotation. The screw jaws can be designed to establish and maintain a frictional or positive locking connection with the screw closure. A high-helix screw drive can translate the robot's pushing motion into a rotation of the screw head and, by means of an adjustable slip clutch, limit the generated torque and simultaneously the pushing force until the high-helix screw drive is engaged – i.e., the high-helix nut is moved to its lower end position on the high-helix screw.

[0020] Once a positive connection with the screw cap is established, the locking mechanism can maintain this positive connection without the application of an external force or energy. This is achieved by the star wheel engaging in short grooves that prevent the star wheel and its associated plunger from sliding completely back towards the screw cap. Upon engaging these short grooves, the locking mechanism of the high-helix screw is also released by actuating an eccentric mechanism in the upper part of the plunger. This mechanism allows the high-helix nut to slide back into its upper end position (the starting position for the next screwing operation) on the high-helix screw spindle due to the force of gravity acting on the screw head body.The screw head body rotates until the high-helix screw drive reaches its home position, as the sliding friction of the high-helix spindle is generally lower than the braking torque of a freewheel in the freewheeling direction, for example, in a positive-locking pawl design. A compression spring in the screw head body can generate the necessary compressive force, which is required both to secure the positive-locking connection and to return the screw jaws to the open position, i.e., the released screw closure.The compression spring can be designed such that, on the one hand, the minimum compressive force required to secure the positive-locking connection is greater than the maximum compressive force required for screw head rotation by the high-helix drive, and on the other hand, the maximum compressive force "F" required to return the screw jaws to the open position is less than the maximum permissible axial force for the screw container due to its limited stiffness. To accommodate a wide range of screw containers with varying stiffness, the compression spring can be made interchangeable and its preload adjustable.Adjusting the overall length and pitch of the lead screw drive to the specific screw container being processed is not strictly necessary, as the freewheel allows the robot to perform a kind of pumping motion. This allows the screw cap to be tightened to a specific torque in several strokes, similar to the acceleration of a spinning top, in a unidirectional rotation. The largest possible pitch can be selected to achieve an advantageous ratio of high torque to low axial thrust.

[0021] The screw lock is released by opening the screw jaws after tightening, once the high-helix screw drive has reached its lower end position. During tightening, only a compressive force acts externally on the screw head to generate the limited torque via the high-helix screw drive. Unintentional unlocking in this state can be prevented by an appropriate compression spring design, torque limitation, and a high pitch of the high-helix screw spindle. A subsequent increase in the compressive force "F" above the switching threshold of the locking mechanism to return the screw jaws to the open position releases the locking mechanism by moving the guide hub relative to the stationary switching star towards the screw lock, thus bringing the switching star into the connection area of ​​the short and long grooves.A partially engaged Hirth tooth on the shift star and the control hub causes the now-free shift star to rotate at the junction of the short and long slots. This rotation continues until the Hirth tooth is centered and thus fully engaged. This ensures that the shift star rotates sufficiently to enter the guide area of ​​the adjacent slots of the guide hub—in this case, the long slots—when the pressure on the screw head is released. During this process, the Hirth tooth is completely disengaged from its self-centering position, and the tooth tips of both parts overlap until the tooth engagement is partially reversed. The axial force required to rotate the shift star relative to the control hub can be generated by a compression spring acting on the control hub, thereby forcing the Hirth tooth engagement and centering of both components.The alignment and counter-support of the control hub within the guide hub can be achieved, for example, via a splined connection with wedge flanks.

[0022] Once unlocked by pressure relief, the screw head is moved away from the screw cap, allowing the plunger to return to its initial position at the end of the long grooves. This causes the screw jaws to pivot away from the screw cap, releasing it. Simultaneously, an eccentric mechanism at the upper end of the plunger, for example, in the form of at least one ball, locks the high-helix drive in its lower end position. This mechanism, via a groove in the axially movable plunger, pushes the ball radially out of the high-helix rod into a corresponding groove in the high-helix nut, thus positively locking the nut against the threaded rod and preventing it from sliding back into its upper position due to gravity.Since the lead screw is still in the lower position "on the stop", a downward-acting pressure force is transmitted, allowing the next screw cap to be gripped without any superimposed torque. Only after the next screw cap has been gripped does the lead screw unlock again and slide back into its upper position – the starting position of the screw head for the next screwing operation.

[0023] The at least two screw jaws can be designed as one-piece, two-piece, or multi-piece components and contain rolling and sliding bearings that facilitate pivoting within the screw head body and rolling on the contoured plunger. Interchangeable contact elements, which may include a negative impression of a possible screw closure knurling to create a positive fit, expand the screw head's range of applications.

[0024] At least two screw jaws can be supported in their opening movement by an O-ring at the level of the area in contact with the plunger.

[0025] The Fig. 1 to Fig. Figure 4 shows the functioning of a possible embodiment of the screw head according to the invention.

[0026] The function of the screw head can be described as follows: The screw head (1) is placed by a robot onto a screw cap (4), which rests with the opening facing downwards on a fixed support, and is moved further towards it by applying a pressure force "F" in order to travel a defined path "X" of the plunger (5) relative to the screw head body (2). During this process, the screw jaws (3) pivot towards the axis center of the screw head and establish a frictional connection with the screw cap (4), while the lead screw (7) is locked in its lower end position and transmits the robot's pressure force without converting it into torque.

[0027] After the screw jaws (3) of the screw head (1) have securely clamped the screw cap (4), the locking mechanism (6) is blocked when the screw head is lifted after traveling the defined distance "X", and the screw jaws (3) remain in the closed position. This functionality is commonly found in ballpoint pens with push buttons and can be applied to the screw head described here. The locking of the high-helix drive (8) by an eccentric mechanism (8.3) is released after the screw head is lifted, so that the screw head body moves downwards due to gravity, or the high-helix nut (8.2) slides into its upper end position on the high-helix spindle (8.1).The robot then moves the screw head with the clamped screw cap towards a screw container, aligns it coaxially, lowers it onto the container, and, after contact, exerts a pressing force which is converted into rotation by the high-helix screw drive (8). Such functionality is commonly known from spinning tops and drill bits and can be applied to the screw head described here. In the solution according to the invention, the high-helix screw drive (8) can be combined with a freewheel (7) so that the advantage of a significantly larger pitch than the screw thread is not negated by the disadvantage of a correspondingly long high-helix screw spindle (8.1). A freewheel has the advantage that, by performing several strokes, successive unidirectional rotary movements of the screw head can be carried out without reversing the direction of rotation, comparable to the acceleration of a spinning top.Furthermore, an additional turn of the screw head is usually necessary, as screw caps do not always engage immediately upon insertion under axial pressure if they are misaligned. Once the screw cap reaches its end position after several strokes, the torque increases until it reaches the set threshold of the torque-limiting slip clutch (9). From this point onward, the screw head no longer rotates, while the helix nut (8.2) continues to move linearly to its lower end position, causing the coupling half (9.1) connected to the helix spindle (8.1) to slip. After the helix drive reaches its lower end position, the robot increases the applied pressure beyond the switching threshold to release the screw jaws and lock the helix drive via an eccentric mechanism (8.3).Upon reaching this state, the robot ceases to apply the pressure force “F” so that the locking mechanism (6) releases the plunger (5) connected to the switching star (6.2), which simultaneously opens the screw jaws (3) to release the screwed closure and locks the steep screw drive (8) in its lower end position.

[0028] Creating a positive-locking connection between the screw jaws and a screw cap requires applying a defined axial force "F" to the screw head. The locking mechanism's switching point is reached after a defined axial displacement "X" of the plunger, and this switching point can be adjustable. Conical screw caps facilitate achieving a defined positive-locking connection at a specific axial switching point of the plunger because, upon contact, the screw jaws generate an immediate force when pivoting onto a conically approaching conical surface. The minimum clamping force required for tightening, i.e., for transmitting torque to the screw cap, is a defined value that can be achieved by pivoting the screw jaws towards the center of the axis, i.e., towards the screw cap.This clamping force can be generated by a specific radius increase with a conical transition on the plunger, as well as the leverage of the pivoting screw jaws, using elastic pads between the screw jaws and the screw cap, known as screw rubbers. The thickness and elasticity of the screw rubbers influence the achievable clamping force. Thus, by varying the thickness and elasticity of interchangeable screw rubbers, a wide variety of screw cap geometries can be processed. Furthermore, it is possible to provide interchangeable screw rubbers or interchangeable screw jaws with a negative imprint of the screw cap's knurling to further increase the transmissible torque on the screw cap by creating a positive fit, which is particularly important for screw caps with a tamper-evident ring.By defining the opening and closing of the screw jaws, particle-generating wear of the screw rubbers can be largely prevented.

[0029] After the screw jaws (3) have gripped and clamped the screw cap (4), this state must be reliably maintained while the screw head is lifted from the base until it is tightened to a defined tightening torque. For this purpose, it is proposed to control the plunger (5) with the switching star (6.2) via a locking mechanism (6). Such a mechanism is commonly found in ballpoint pens with a push button and can be constructed similarly in the screw head (1) described here. When the screw head (1) with the plunger (5) is pressed centrally onto a screw cap (4), the switching star (6.2), which is rotatably mounted on the plunger (5), is released after a defined travel distance "X" in the transition area between the long and short grooves (6.3) of the guide hub (6.1). The switching star is held in place by the control hub (6.1), which is under axial spring preload.4) The Hirth toothing is rotated until it engages in the short grooves (6.3) during the subsequent pressure relief of the screw head. Release of the gripped screw closure is geometrically blocked in the short grooves because the rolling bearings of the screw jaws remain on the large diameter of the plunger (5) and thus maintain the closed state of the screw jaws (3).

[0030] The locking mechanism allows the screw cap (4) to be held by the screw jaws (3) without the supply of an external force or form of energy and to be screwed onto a screw container by applying a pressure force, which is converted into a limitable screwing torque by means of the steep screw drive (8), a freewheel (7) and an adjustable slip clutch (9).

Claims

[1] Screw head (1), in particular for a robot, comprising a screw head body (2) on which at least two pivotably mounted screw jaws (3) are arranged, which can selectively assume an open position or a closed position for gripping and screwing screw closures (4), such that in the closed position the screw closure (4) is gripped and can be screwed and in the open position the screw closure (4) is released, characterized byA combined gripping and rotational mechanism with limitable torque and freewheel, consisting of an actuator (5) mounted axially movable centrally in the screw head (1) and a gearbox (6) cooperating with the actuator (5), which is designed to convert a movement of the actuator (5) triggered by pressing the actuator (5) against the screw cap to be gripped into a closing movement of the at least two screw jaws (3) in order to grip the screw cap (4), and a steep-pitch screw drive (8) with freewheel (7) and slip clutch (9), which is designed to convert a movement of the screw head triggered by pressing the screw head in the closed position of the screw jaws with the screw cap gripped against a screw container into a rotational movement of the screw head base body in order to screw the screw cap (4) onto a screw container. [2] Screw head according to claim 1, characterized by, that the gearbox (6) is designed as a locking tensioning device and is combined with a steep screw drive (8), a freewheel (7) and an adjustable slip clutch (9). [3] Screw head according to claim 1 or 2, characterized by , that the transmission (6) has a rotationally symmetrical volume element connecting the actuator (5) with the at least two screw jaws (3), in particular with a conical shoulder (5.1), which is designed to transmit the movement of the actuator (5) to the at least two screw jaws (3) and in its extension to lock and unlock the steep screw drive (8) via an eccentric mechanism (8.3). [4] Screw head according to one of claims 1 to 3, characterized by, that the gearbox (6) has a locking mechanism for blocking the movement of the screw jaws (3) at least from the closed position of the screw jaws (3) to the open position of the screw jaws (3) and for unlocking the steep screw drive (8), such that the screw jaws (3) are locked autonomously in a clamping state holding the screw closure (4) and at the same time the steep screw drive (8) is unlocked, such that a pressure force exerted on the screw head is converted into a rotary movement of the screw head with a torque that can be limited via an adjustable slip clutch (9) for screwing the closure. [5] Screw head according to any one of claims 1 to 4, characterized by, that the gearbox (6) has a release mechanism for unlocking the screw jaws (3) and for locking the steep screw drive (8), such that the screw jaws (3) can be moved from their closed position to their open position in order to release the screw closure (4) and simultaneously lock the steep screw drive (8), such that a pressure force applied to the screw head is transmitted without being converted into a rotational movement of the screw head. [6] Screw head according to any one of claims 1 to 5, characterized by, that the transmission (6) has a cam guide (6.1) and a cam block (6.2) guided in the cam guide, wherein the cam guide (6.1) has a first track section (6.3) configured to block the movement of the screw jaws (3) from the closed position to the open position and to release the locking of the helix screw drive (8) in a state in which the cam block (6.2) is located in the first track section (6.3), and has a second track section configured to release the movement of the screw jaws (3) from the closed position to the open position and to establish the locking of the helix screw drive (8) in a state in which the cam block (6.2) is located in the second track section. [7] Screw head according to any one of claims 1 to 6, characterized by, that each screw jaw (3) has a first area (3.1), a second area (3.2) and a third area (3.3), wherein the first area (3.1) is in contact with the screw cap for gripping and screwing, the second area (3.2) is designed as a pivot bearing between the first and the second, and the third area (3.3) is in contact with the actuator (5) and translates an axial compressive force into a clamping force acting radially towards the center of the axis on the screw cap (4). [8] Screw head according to any one of claims 1 to 7, characterized by , that a pressure force acting externally in the axis of rotation is converted into a rotary movement for screwing screw caps (4) onto screw containers by means of a steep screw drive (8) and an adjustable slip clutch (9) to limit the torque. [9] Screw head according to any one of claims 1 to 8, characterized by, that the steep screw drive (8) is combined with a freewheel (7) to generate a unidirectional direction of rotation for screwing screw caps (4) onto screw containers.

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