EP0935584B1 - Threaded joint spindle with adjustable clamping moment - Google Patents

Abstract

The invention concerns a threaded joint spindle comprising a spindle shaft (5) provided with a prehensile device (6) and integral with a pinion (7) driven in rotation by a motor set (11) which comprises a cylinder (17) with a rod secured to a transmission member (12, 14, 15, 16), and a member for adjusting pressure (21) arranged on a line supplying (22) the cylinder in a screwing direction.

Description

The invention relates to a screwing spindle with adjustable tightening torque, especially for setting place by screwing caps on packaging with threaded necks.

Known screw pins have a electric or pneumatic motor driving in rotation a shaft one end of which is fitted with a gripping plugs. The spindle tree is by elsewhere animated by a vertical movement allowing the setting in contact with the cap and screwing onto a threaded neck.

One of the concerns related to these pins relates to the control of the applied torque at the cap. It is indeed important that this couple is sufficiently important to ensure an effective closure of packaging and avoid any untimely loosening of the plug closing it, without the user must use a tool to open the package. A torque limiting device must therefore be interposed between the motor and the spindle shaft in order to transmit a specified tightening torque.

We know, in particular documents US 4,756,137 and EP 387,153, torque limiting devices to friction comprising two plates pressed one against the other. But the friction between the two plates cause significant wear of these and overheating modifying their coefficient of friction. The The transmitted tightening torque is therefore not constant. he there are also torque limiting devices magnetic not having the aforementioned drawbacks. However, these devices also have torque adjustment problems, especially due to aging of the magnetic elements and, in the case permanent magnets chatter occurs when slip.

To overcome these drawbacks, we plan, according to the invention a screw spindle comprising a shaft spindle provided with a gripping device and integral a pinion pinion rotated by a jack having a rod integral with a transmission member arranged to actuate the pinion, and an adjusting member pressure arranged on a cylinder supply line in a screwing direction.

Thus, the tightening torque being directly function of the force applied by the cylinder and this one being a direct function of the supply pressure of the cylinder by pressurized fluid, the tightening torque is determined by the cylinder supply pressure so that it simultaneously performs the functions of organ motor and torque limiter.

The pins according to the invention are therefore more simple and less expensive than screwdriver pins current.

Another advantage of the invention lies in the causes the adjustment of the tightening torque by several spindles of a multispindle turret can be realized by acting on a pressure adjusting device common power supply for all these pins. We avoid thus at the level of each spindle tedious handling and source of an increasing risk of error with the number of turret pins. This pressure setting supply can also be achieved when the turret is in operation. The invention thus increases the reliability and profitability of such turrets.

According to an advantageous embodiment of the invention, the transmission member comprises a rack.

Advantageously, the rack extends parallel to the longitudinal axis of the spindle shaft and the transmission member comprises a return pinion angle. The screw spindle according to the invention is thus particularly compact.

According to a preferred embodiment of the invention, the transmission member comprises a free wheel mounted to drive the device unidirectionally gripping in a screwing direction. So we can return the cylinder to the retracted position before releasing the plug gripper so that at the time of the release of the gripping device it is ensured that the spindle is not subjected to any torque and this is avoided scratch the plug during this release.

Advantageously, the jack is secured in translation of the spindle shaft.

This arrangement improves the compactness of the screw spindle according to the invention.

According to another characteristic of the invention, the transmission member comprises a toothed wheel having a diameter greater than that of the pinion. This allows multiply the number of spindle turns for a given stroke of the cylinder.

According to an advantageous version of the invention, at least one sensor is arranged to detect a position of the cylinder rod.

The addition of one or more sensors position of the rod allows a check of the progress of the screwing operation. Indeed, too much displacement of the stem can reveal an absence of plug, while that a too small displacement, while the torque of tightness is reached, may indicate a plug engaged obliquely on the neck of the packaging. We obtain thus a simple and inexpensive way to ensure the quality of screwing.

Other characteristics and advantages of the invention will appear again on reading the description which follows of a particular nonlimiting embodiment of the invention in relation to the single figure attached representing a partial perspective view of a pin of screwing according to the invention.

Referring to the figure, the screw pin according to the invention comprises a vertical guide tube 1, the upper end of which is fixed to a support spindle 2 and which slides vertically in a sleeve 3 integral with a rotary platform 4. The tube 1 receives at rotation a spindle shaft 5 whose lower end protrudes from tube 1 and wears a gripping device jaws 6 actuated in a manner known per se. The end upper part of spindle shaft 5 carries a bevel gear 7 cooperating with an engine assembly generally designated as 11.

Spindle holder 2 is mounted to slide on a column 9 fixed to the rotary platform 4 and carries a roller 8 intended to cooperate with a cam (not shown) to position the support 2 in height and the parts associated with it.

A support plate 10 is fixed on the side of the spindle support 2 and carries the motor assembly 11.

The motor assembly 11 comprises an intermediate shaft 12 rotatably mounted in a bearing 13 carried by the support plate 10. The shaft 12 has one end bearing, by via a free wheel 20, a return pinion conical 14 whose teeth are in contact with those of the pinion 7, and an opposite end carrying a pinion input 15 whose teeth are in contact with those of a rack 16. rack 16 extends vertically and is fixed by its lower end to the rod of a jack 17 of vertical axis whose body is fixed to the plate support 10. The jack is connected to a device for adjusting pressure 21 arranged on a supply line 22 for supply the jack 17 in a direction of screwing the plugs.

A support roller 18 with a parallel axis of rotation to that of the input pinion 15 is pivotally mounted at the end upper of the support plate 10 and is arranged substantially opposite the input pinion 15 on one side of the rack opposite to it so that the rack 16 is kept applied against the pinion input 15.

A sensor 19 is attached to the upper end of the support plate 10 at the extreme position of rack 16, for a fully extended position cylinder rod 17.

In operation, the platform 4 is driven in rotation relative to a fixed frame by a motor. Of threaded neck packages are brought in and held plumb with the jaw gripping device 6 by a device not shown.

Support 2 and all the elements that are attached to it associated constitute a mobile assembly in translation vertical but linked in rotation to the platform 4. The vertical positioning of this mobile assembly is ensured by the contact of the roller 8 on the cam track and depends so the profile of the latter.

While a threaded neck package is being fed perpendicular to the gripping device 6, the latter is actuated in a manner known per se to grasp a plug on a distributor not shown. The roller 8 according to the profile of the cam path of the frame then causes the descent from the mobile assembly to the threaded neck.

Once the cap is in contact with the neck threaded, a fluid under a pressure preset by means of the pressure adjusting member 21 is brought to the jack 17. The rod of the jack 17 pushes the rack 16 upwards. The rack 16 rotates the input pinion 15. The input pinion 15 transmits its movement to the gripping device 6 via the shaft 12, pinions 14 and 7, and spindle shaft 5 pivoting in the guide tube 1. Note in this connection that the freewheel 20 is mounted so that the jack 17 drives spindle shaft 5 in the direction of screwing but does not drive not it in rotation when the cylinder 17 retracts. The pinion 14 preferably has a diameter greater than pinion 7 in order to obtain a screwing on several turns for a short stroke of the jack 17, which makes it possible to use a cylinder having a reduced bulk.

When the tightening torque of the plug causes a resistant torque having a value equal to that of engine torque resulting from the supply pressure of the cylinder 17, the screw spindle stops rotating and the rack 16 stops. For an angular position of the platform corresponding to the end of the tightening cycle on cylinder is retracted, either by a power reversal when the cylinder is a double-acting cylinder, either by simple power cut and an elastic reminder in the case of a single acting cylinder. Due to the wheel mounting free from the pinion 14, the spindle shaft 5 remains stationary. The jaws of the gripping device 6 can then be open without risking scratching the cap. The brooch screwing is raised and the assembly is ready for a new one cycle.

The sensor 19 is placed at the end of the stroke of the rack beyond the distance that the rack 16 should normally cover to achieve the number of rounds required for capping.

If the rack 16 is detected by the sensor 19, this means that the tightening torque corresponding to supply pressure was not reached due an absence of a stopper, a defective stopper, or a packaging whose neck is damaged.

The sensor 19 then controls the conveying of the packaging not properly sealed to a waste circuit.

When we want to ensure the closure of a new series of packages for which we want a couple of different tightening from that used previously, just to change the setting of the supply pressure of the cylinder 17.

The invention is not limited to the embodiment described, but also includes any variant including, with equivalent means, the characteristics essentials of the invention as defined by claims.

In particular, although the freewheel 20 has been illustrated between the intermediate shaft 12 and the pinion 14, we could have this freewheel at any point of the kinematic chain connecting the jack 17 to the gripping device 6. It is also possible to provide realize a kinematic chain without freewheel. In this case, it will be necessary to put the jack 17 to the exhaust without retracting it before opening the jaws.

Although rack 16 has been shown in vertical position, it can be positioned horizontally and put it in direct contact with the pinion 7 which, in this case, is preferably a cylindrical pinion.

Although in the embodiment described, had used a rack, we could realize the invention with any mechanism transforming the movement of translation of the rod of the jack 17 in rotational movement to drive the spindle shaft 5, for example a mechanism rod-crank type.

Claims (7)

1. A screwdriving spindle assembly comprising a spindle shaft (5) provided with a holding device (6) and secured to a gear wheel (7) rotated by a drive assembly (11), said spindle assembly being characterized in that the drive assembly (11) comprises a pressurized fluid actuating cylinder (17) having a piston rod secured to a transmission system (12, 14, 15, 16) disposed to drive the gear wheel, and a member for adjusting pressure (21) disposed on a line (22) for feeding fluid to the cylinder in the screw-tightening direction.
2. A spindle assembly according to claim 1, characterized in that it includes a free-wheel (20) mounted to drive the holding device (6) in a screw-tightening direction only.
3. A spindle assembly according to claim 1, characterized in that the transmission system (12, 14, 15, 16) includes a rack (16).
4. A spindle assembly according to claim 3, characterized in that the rack (16) extends parallel to the longitudinal axis of the spindle shaft (5), and the transmission system (12, 14, 15, 16) includes a gear wheel (14) for transmitting drive through an angle.
5. A spindle assembly according to claim 1, characterized in that the shaft of the spindle is movable in translation, and the cylinder (17) is constrained to move in translation with the spindle shaft (5).
6. A spindle assembly according to claim 1, characterized in that the transmission system (12, 14, 15, 16) includes a toothed wheel having a diameter greater than that of the gear wheel.
7. A spindle assembly according to claim 1, characterized in that at least one sensor (19) is disposed to detect a position of the cylinder piston rod (17).

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