SCREW SYSTEM

Abstract

The invention relates to a screw system for carrying out screwing operations, in particular automatically, with a screwing tool and a feed device having a pneumatic feed cylinder by means of which the screwing tool is movable in a feed direction in order to be brought into engagement with a screw and to drive the latter into components to be screwed together with a first feed force during a screwing operation.

Claims

1-11. (canceled)

12. A screwing system for carrying out screwing procedures, the screwing system comprising a screwing tool and a feed device having a pneumatic feed cylinder by means of which the screwing tool is movable in a feed direction to be brought into engagement with a screw and to drive the screw into components to be screwed with a first feed force during a screwing procedure, wherein the feed device comprises a pressure intensifier by which a second feed force, which is larger than the first feed force, can be exerted onto the screwing tool during the screwing procedure.

13. The screwing system in accordance with claim 12, wherein the screwing system is configured for an automatic carrying out of screwing procedures.

14. The screwing system in accordance with claim 12, wherein the pressure intensifier can be switched on and off at any desired time of the feed movement of the screwing tool.

15. The screwing system in accordance with claim 12, wherein the pressure intensifier can be metered.

16. The screwing system in accordance with claim 15, wherein the feed cylinder has a pneumatically actuable working piston, with the pneumatically actuable working piston being configured to carry out a maximum working stroke and the pressure intensifier being configured to effect a force stroke of the working piston which is smaller than the maximum working stroke.

17. The screwing system in accordance with claim 15, wherein an actuation piston of the pressure intensifier is arranged coaxially with or offset from the pneumatically actuable working piston.

18. The screwing system in accordance with claim 15, wherein a force transmission from an actuation piston of the pressure intensifier onto the pneumatically actuable working piston takes place by means of a hydraulic fluid.

19. The screwing system in accordance with claim 12, wherein an actuation piston of the pressure intensifier is configured to be pneumatically actuated.

20. The screwing system in accordance with claim 19, wherein the actuation piston of the pressure intensifier is configured to be metered by the pneumatic actuation pressure.

21. The screwing system in accordance with claim 12, wherein the pressure intensifier is a pneumatic, a hydraulic or a pneumohydraulic pressure intensifier.

22. The screwing system in accordance with claim 12, wherein the feed device only moves the screwing tool or moves the screwing tool together with a torque measuring device and/or with a drive unit.

23. The screwing system in accordance with claim 12, further comprising a feed head for holding the screw in a position aligned for the engagement of the screwing tool.

24. The screwing system in accordance with claim 23, further comprising a feed device for the automatic supply of screws into the feed head.

25. The screwing system in accordance with claim 12, further comprising a feed device for the automatic supply of screws into a feed head.

Description

[0017] The invention will be described in the following purely by way of example with reference to a possible embodiment and to the enclosed drawing. There is shown:

[0018] FIG. 1 a schematic, partly sectional side view of a screwing system in accordance with the invention.

[0019] A screwing system in accordance with the invention is shown schematically in FIG. 1 which can, for example, be installed at a robot arm or statically at a rack to carry out flow-drilling screwing procedures automatically.

[0020] The screwing system comprises a screwing tool 10 which defines a central longitudinal axis 11 and is rotationally drivable about the central longitudinal axis 11 by means of a rotary drive 12. A torque measuring device 14 is connected between the screwing tool 10 and the rotary drive 12.

[0021] The screwing system furthermore comprises a guide 16 which extends in parallel with the central longitudinal axis 11 of the screwing tool 10 and on which a supply head 18 is displaceably supported which can be traveled along the guide 16 by means of a delivery cylinder 20 to be brought into contact with a component to be screwed. The supply head 18 serves for the alignment and holding of a screw provided for the screwing procedure and not shown in the Figure. To supply the screw into the supply head 18, the latter is coupled to an automatic supply device, likewise not shown, which, for example, shoots the screw into the supply head 18 by means of compressed air.

[0022] To bring the screwing tool 10 into engagement with the screw held in the supply head 18, the screwing tool 10 is pushed forward, together with the torque measuring device 14, out of the rear end position shown in FIG. 1, which can also be called a position of rest, to the front, that is to the left in FIG. 1. A feed device 22 serves this purpose which acts on the torque measuring device 14 which is in turn displaceably supported on the guide 16.

[0023] The feed device 22 comprises a pneumatic feed cylinder 24 having a working piston 28 which is oriented in parallel with the screwing tool 10 and with the guide 16, which can be actuated by means of compressed air 26 and which can carry out a maximum working stroke predefined by the length of the feed cylinder 24. The working piston 28 is coupled to the torque measuring device 14 and can e.g. be molded onto a housing of the torque measuring device 14.

[0024] The working piston 28 is furthermore configured as hollow cylindrical and is displaceably supported on a pipe piece 30 which extends from the rear, that is from the right in FIG. 1, into the working piston 28. The inner space 37 bounded by the pipe piece 30 and by the working piston 28 is filled with a hydraulic fluid and is sealed with respect to an air space 36 of the feed cylinder 24 by means of seals 34.

[0025] The inner space 32 has a first cross-sectional surface and opens at its rear end into a fluid storage space 38 which is likewise filled with hydraulic fluid and has a second cross-sectional surface which is larger by a multiple than the cross-sectional surface of the inner space 32. The fluid storage space 38 is bounded at the rear side by a displaceably supported ring piston 40 which is urged to the front, i.e. in the direction of the feed cylinder 24, by an equalizing spring 42. The inner space 32 and the fluid storage space 38 together form a hydraulic system closed in itself.

[0026] A plunger 44 which is coaxially aligned with the pipe piece 30 extends through the ring piston 40 and its profile is adapted to the profile of the pipe piece 30 such that it can dip sealingly into the pipe piece 30, with the sealing effect being additionally improved by a seal 46 arranged in the end region of the pipe piece 30.

[0027] The plunger 44 is part of an actuation piston 48 which is displaceably supported in a force cylinder 50 and which can be actuated by means of compressed air 52. The sealing of an air space 54 of the force cylinder 50 with respect to the fluid storage space 38 takes place by means of seals 56 which are let into the ring piston 40.

[0028] The plunger 44 is surrounded by a return spring 58, here in the form of a helical compression spring, which is supported at a rear side of the ring piston 40, on the one hand, and at a front side of the actuation piston 48, on the other hand, and which urges the ring piston 40 and the actuation piston 48 apart. Alternatively, the return spring 58 can be configured in the form of a pneumatic spring.

[0029] The components 30 to 58 together form a pneumohydraulic pressure intensifier 60 of the feed device 22 whose function will be explained in the following.

[0030] To bring the screwing tool 10 out of its position of rest shown in FIG. 1 into engagement with a screw held in the supply head 18, the feed cylinder 24 has compressed air 26 applied such that the working piston 28 is moved to the left in FIG. 1 and in so doing pushes the torque measuring device 14 and the screwing tool 10 to the front. When the screwing tool 10 is in engagement with the screw, the screwing tool 10 is pushed further forward by the feed cylinder 24 actuated by compressed air until the screw adjoins the component to be screwed.

[0031] The inner space 32 increases due to the movement of the working piston 28 to the front, with hydraulic fluid being urged on into the inner space 32 from the fluid storage space 38 by the ring piston 40 acted on by the equalizing spring 42.

[0032] Since the force which can be applied onto the feed cylinder 24 by the compressed air 26 is not sufficient to introduce a heat sufficient for the flow-drilling screwing procedure into the component to be screwed within a time acceptable for an economic screwing procedure, the pressure intensifier 60 is activated as soon as the screw adjoins the component to be screwed.

[0033] This is done in that compressed air 52 is applied to the actuation piston 48 and the plunger 44 is thereby pushed to the front. As soon as the plunger 44 dips into the pipe piece 30, the inner space 23 is sealed with respect to the fluid storage space 38 and hydraulic fluid can no longer escape from the inner space 32 or flow on into it. A further application of compressed air 52 to the actuation piston 48 now has the effect that a second feed force is exerted onto the screwing tool 10 via the working piston 28, said second feed force being substantially larger than the first feed force which can be exerted onto the working piston 28 by the compressed air 26. Under the assumption that the compressed air 52 acting on the actuation piston 48 is at the same pressure as the compressed air 26 acting on the working piston 28, the ratio of the second feed force to the first feed force approximately corresponds to the ratio of the cross-sectional surface of the actuation piston 48 to the cross-sectional surface of the plunger 44.

[0034] The pressure of the compressed air 52 can be controlled, e.g. by a pneumatic proportional valve controlled by a control, to meter the second feed force.

[0035] It is understood that the pressure intensifier 60 is dimensioned such that the second feed force is sufficiently large to heat the component to be screwed within a time acceptable for the process procedure to a temperature sufficiently high for the flow-drilling screwing.

[0036] As soon as the component has reached a sufficient flow capability, the screw is driven into the component with a further feed of the screwing tool 10. After reaching a sufficient flow capability of the component, it is generally possible to deactivate the pressure intensifier 60 again in that the supply of the compressed air 52 is stopped and the plunger 44 is drawn out of the pipe piece 30 again by the return spring 58 such that the hydraulic fluid can again flow on out of the fluid storage space 38 into the inner space 32, while the feed of the screwing tool 10 during the remaining phase of the screw procedure is implemented by applying compressed air 26 to the working piston 28. It is, however, generally also conceivable to carry out the whole screwing procedure with the pressure intensifier switched on provided that it can carry out a sufficiently high stroke, with the second feed force also being able to be metered here by the use of a pressure-regulated control pressure of the pressure intensifier 60.

[0037] It must finally be pointed out that the arrangement of the pressure intensifier 60 relative to the feed cylinder 24 shown in FIG. 1 is only of a schematic nature. The pressure intensifier 60 thus does not necessarily have to be coaxially aligned with the feed cylinder 24. For a more compact construction size of the screwing system, the pressure intensifier 60 can, for example, also be arranged offset in parallel with the feed cylinder 24 and can even act in the opposite direction. In the latter case, the pipe piece 30 could form the one limb of a U-shaped hydraulic passage, while the plunger 44 dips in the other limb of the U-shaped hydraulic passage on activation of the pressure intensifier 60.

REFERENCE NUMERAL LIST

[0038] 10 screwing tool

[0039] 11 central longitudinal axis

[0040] 12 rotary drive

[0041] 14 torque measuring device

[0042] 16 guide

[0043] 18 supply head

[0044] 20 delivery cylinder

[0045] 22 feed device

[0046] 24 feed cylinder

[0047] 26 compressed air

[0048] 28 working piston

[0049] 30 pipe piece

[0050] 32 inner space

[0051] 34 seal

[0052] 36 air space

[0053] 38 fluid storage space

[0054] 40 ring piston

[0055] 42 equalizing spring

[0056] 44 plunger

[0057] 46 seal

[0058] 48 actuation piston

[0059] 50 force cylinder

[0060] 52 compressed air

[0061] 54 air space

[0062] 56 seal

[0063] 58 return spring

[0064] 60 pressure intensifier