Pneumatic strapping apparatus

Abstract

A pneumatically actuated strapping apparatus for strapping plastic tape around a packaging item including a motorized tensioning device and a motorized welding device for the plastic tape. The tensioning device and the welding device are driven by the same pneumatic motor. The direction of rotation of the pneumatic motor can be inverted. The pneumatic motor is connected to the devices by two freewheeling mechanisms releasing the devices in opposite directions. In order to keep power consumption for evacuating non-operational air low, in a particularly preferred embodiment, switching valves which automatically discharge the nonoperational air to the exterior are integrated into the air intake ducts that are used as evacuation ducts for the non-operational air when the direction of rotation is inverted.

Claims

1. A pneumatically actuated strapping apparatus for strapping a plastics tape around a package, comprising: a motorized tensioning device; a motorized welding device for the plastics tape, wherein the motorized tensioning device and the motorized welding device are operatively coupled to and driven by a same pneumatic motor, wherein the pneumatic motor is reversible and comprises two inlet air ducts which are alternatively subjected to compressed air flowing in a first direction, each inlet air duct having respective integrated reversing valves disposed therein which automatically vent directly outward in the event of an air flow that is in an opposite direction of the first flow direction.

2. The strapping apparatus as claimed in claim 1, wherein the pneumatic motor can be operatively connected alternatively to the motorized tensioning device or the motorized welding device via freewheels, the freewheels permitting free movement in opposite directions.

3. The strapping apparatus as claimed in claim 1, wherein the pneumatic motor comprises a motor shaft protruding from both ends of the pneumatic motor, wherein each shaft end is connected to one of the freewheels, respectively, the freewheels permitting free movement in opposite directions.

4. The strapping apparatus as claimed in claim 1, wherein each reversing valves includes a respective cross-sectionally substantially M-shaped switching diaphragm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and features of the invention emerge from the following description of an illustrative embodiment, wherein:

(2) FIG. 1 shows the working head of a pneumatically operated strapping apparatus in perspective view;

(3) FIG. 2 shows the side view of a pneumatic drive motor for a working head according to FIG. 1;

(4) FIG. 3 shows a sectional view along the line A-A in FIG. 2;

(5) FIG. 4 shows a sectional view along the line B-B in FIG. 2; and

(6) FIG. 5 shows a sectional view along the line C-C in FIG. 2.

DETAILED DESCRIPTION

(7) In FIG. 1, the perspective view of the working head of a pneumatically actuated strapping apparatus can be seen. Mounted on this working head is a handle 2, by means of which the strapping apparatus is handled. Beneath this handle is here found an actuating lever 3, by means of which, together with the actuation of push buttons 4, the pneumatic strapping apparatus is controlled.

(8) In the use of the strapping apparatus, a plastics tape is guided through a slot 6 situated on the away-facing side in FIG. 1. The plastics tape is then placed around a package to be strapped and is then guided once again through the slot 6. The plastics tape is thus placed in a loop around the package.

(9) The plastics tape is then tautened via a motorized friction wheel, so that it lies tightly around the package. Finally, the plastics tape, at a position within the strapping apparatus on which it overlaps after formation of the loop, is then compressed to form a connecting point

(10) At this position, a vibrating plate is then lowered onto the clamped-together bands and this vibrating plate is set in vibration by motorized means. Due to this vibration, there ensues a relative movement at the connecting point between the two overlapping tape portions and, owing to the friction which is hereupon generated, a local fusion of the thermoweldable plastics tape.

(11) Finally, this welded connecting point can then cool down, so that a solid welding point is formed and the strapping apparatus can be removed from the packing tape, whereupon the packing tape slides out of the slot 6.

(12) The above-discussed friction wheel is driven via a bevel gearing 7 by a pneumatic motor 8. In FIG. 1 is represented a housing 9, which normally fully covers the bevel gearing 7 and the pneumatic motor 8, but here, for better clarity, is broken open and partially omitted.

(13) At its end lying axially opposite the bevel gearing 7, the pneumatic motor 8 bears a further gearwheel 10, via which it can be connected in a known manner to the vibration drive for the welding or vibrating plate.

(14) The motor is mounted, for easier assembly, on a base plate 11. The easy exchangeability thereof also facilitates the assembly and subsequent maintenance of the strapping apparatus.

(15) In FIG. 2, the base plate 11, with pneumatic motor mounted thereon and the bevel gearing 7 likewise mounted thereon, is represented in side view. In FIG. 2 can also be seen the gearwheel 10, which is likewise seated on the pneumatic motor 8.

(16) In FIG. 3, which represents a section transversely through the pneumatic motor 8 along the line A-A in FIG. 2, it can be seen that the motor shaft 12 of the pneumatic motor 8 terminates on the two sides of the pneumatic motor in shaft ends 13, 14. On these shaft ends 13, 14 is seated, on the one hand, a bevel wheel 15, which is part of the bevel gearing 7. At the opposite end, the motor shaft 12 bears the above-discussed gearwheel 10.

(17) Both the gearwheel 10 and the bevel wheel 15 do not in this case sit directly on the shaft ends 13, 14, but rather freewheels as drawn cup roller clutches 16, 17 are interposed here.

(18) These two drawn cup roller clutches 16, 17 release the torque transmission in respectively opposite directions of rotation, so that, upon rotation of the pneumatic motor 18 or its motor shaft 12, either the bevel wheel 15, or the gearwheel 10, are co-rotated. The respectively other wheel is disconnected via the interposed drawn cup roller clutches and, accordingly, is not driven. There is thus the possibility of actuating with just one motor 8 either the friction wheel drive or alternatively (but not simultaneously) the vibration drive. Two different places at which power is required can thus be served with just one motor.

(19) For the actuation of the pneumatic motor, compressed air is fed to it, as represented in FIG. 5, via an inlet air port 18. This compressed air flows past a reversing valve 19 (described in greater detail below) through an inlet air duct 20 to the rotor 21 of the pneumatic motor 8. This compressed air sets the rotor 21 in rotation and then flows off from the pneumatic motor 8 via a central outlet 22.

(20) The idle air generated by the rotor 21 in the course of its rotation takes the course represented in FIG. 4. It flows through a duct 23 to a further reversing valve 24 and, at this, is evacuated to the environment directly through an outlet opening 25 provided thereon.

(21) The idle air of the pneumatic motor 8 does not therefore have to be guided through possibly narrow ducts firstly to the central outlet 22.

(22) If the pneumatic motor 8 is now driven in the opposite direction, compressed air is fed to it via another inlet air port 26, which is represented in FIG. 4. The reversing valve 24 closes with its diaphragm 27 the outlet opening 25 and the compressed air then flows through the duct 23, as the inlet air duct, to the rotor 21. The latter is rotated in the opposite direction and the compressed air which drives it then flows off into the environment through the central outlet 22.

(23) At the same time, the idle air which is here generated by the rotor 21 flows through the duct 20 (discernible in FIG. 5) to the reversing valve 12. There, the cross-sectionally substantially M-shaped diaphragm 28 thereof is pressed in front of the inlet air port 18, so that the idle air flows through the reversing valve 19 to an outlet opening 29 provided thereon, where it is discharged to the environment, again without having previously been conducted through possibly narrow ducts firstly to the central outlet 22.

(24) The cross-sectionally substantially M-shaped diaphragms 27, 28 can respectively alternatively close off the inlet air ports 18 and 26, or else the duct portions which in the valves 19 and 24 lead to the outlet openings 29 and 25. At the same time, the diaphragms, with their radially outer sealing lips, make it possible, as represented in FIG. 5, for inlet air in the radially outer region of the reversing valve 19 or 24 to be able to flow past them to the inlet air duct 20 or 23, or else, as represented in FIG. 4, for the idle air which meets the inlet air and flows off from the pneumatic motor to be able to displace the diaphragms for sealing off of the inlet air ports and for simultaneous release of the duct portions to the outlet openings.