Pneumatic strapping tool

Abstract: A compact hand-operated pneumatic strapping tool (1) has a compact arrangement of the sealing (15) and the tension (16) valves, and a combination sealing motor (4) valve module (2) arrangement. A cam driven tooth (13,19) terminates the sealing step. The valve/motor arrangement (24) results in a more compact and lighter weight strapping tool, for drawing a steel strap (8) around a load, and sealing the strap by punching interlocking slits into the strap ends.

Description: The present invention pertains to the field of drawing a steel strap around a load, and sealing the strap in the drawn position. Particularly, the invention relates to lightweight, hand-held tools which accomplish this task. Strapping tools are in use for the purpose of drawing a steel strap around a load, sealing the strap, and cutting the strap. Hand-operated tools have been proposed for addressing this task. However, many prior art tools suffer from shortcomings such as large size, and heavy weight, making them difficult to manipulate by hand. The present invention addresses and solves the problems associated with hand-held strapping tools which are overly heavy and large in size, by proposing a smaller and lighter weight device which performs all of the necessary strapping functions. An example of a hand-held strapping tool is described in EP-A-0720947. Hand-held strapping tools firstly tension the strap around the load and then seal the strap to itself. Ordinarily, the tensioning step is carried out and then, at the direction of the user, the sealing step is commenced. GB-A-1054034 discloses a hand-held strapping tool wherein the sealing step is then automatically terminated at the end of a sealing operation cycle. It would be beneficial if this automatic termination of the sealing step could be achieved in a smaller, lighter and less complex manner. According to this invention a compact hand-operated pneumatic strapping tool having strap tensioning means; sealer means for punching interlocking slits through overlapping strap sections, the sealer means being driven by a pneumatically operated cam shaft; a valve module, the valve module having a sealer valve and a tension valve, the sealer valve controlling a sealer motor, the tension valve controlling a tension motor; and sealer disengagement means for terminating a sealing step after a complete cycle, and having a release cam driven by the cam shaft so that when a strap is tensioned by the strap tensioning means, and sealed by the engagement of interlocking slots punched into overlapping sections of the strap, the sealing step is terminated by the action of the release cam; is characterised in that the sealer disengagement means has a pawl, the pawl having a release tooth surface and a sealer valve support surface, and the release cam has a release cam tooth which acts against the release tooth surface to rotate the pawl in a manner which moves the sealer valve from the ON to the OFF position, causing termination of the sealing step. The present invention addresses and solves the problems existing with prior art strapping machines with respect to overly large size and heavy weight. Specifically, in a preferred example it includes a compact pneumatic valve assembly, and a compact sealing motor valve assembly arrangement with a toothed release cam, driven by the sealer cam, acting to terminate the sealing step. The arrangement of the tensioning and sealing valves with respect to the sealer motor, and the arrangement of the gear package, sealer motor/valve assembly, sealer cams, and tension motor contribute to the compact size, light weight, and reliable operation of the present invention. A preferred example of the present invention will now be described with reference to the accompanying drawings; in which:- FIG.1 is a side view of the strapping tool; FIG.2 is an end view of the strapping tool; FIG.3 is a schematic view of the sealer valve actuation and release mechanism in the sealing mode; FIG.4 is a schematic view of the sealer valve actuation and release mechanism in the non-sealing mode, and, FIG.5 is a perspective view of the pawl. Figures 1 and 2 show an overall view of this example of the present invention. The strapping tool 1 includes a lever module 2 containing a sealer lever 11, a tension lever 12, and tension shut-off switch 10. A sealer valve 15 and a tension valve 16 are housed in a valve module 3. The valve module 3 and the sealer motor 4 are disposed together at the top of the strapping tool 1. A gearbox 5 is disposed in a generally vertical position at one end of the strapping tool. A sealer cam 6 having a plurality of cam surfaces for punching slits into a metal strap, and for cutting the strap, is disposed generally below and parallel with the sealer motor 4/valve module 3 arrangement. A sealer follower module 7 includes cam followers, and punching and cutting elements which are activated by the cam surfaces of the sealer cam 6. A metal strap 8 may be inserted into the strapping tool 1 by rotating in an upward direction the tension motor/gear housing assembly 14. In operation, the strap 8 may be drawn up manually to eliminate excess slack. The tension motor/gear housing assembly 14 is then released so that the tension wheel 9 rests against a top surface of the strap 8. Depressing the tension lever 12 activates the tension valve 16 and the tension motor/gear housing assembly 14, which rotates the tension wheel 9, causing it to move the strap 8 through the strapping tool, drawing the strap 8 to a desired tension level 1. The tension motor/gear housing assembly 14 is designed to stall if a predetermined tension level is exceeded, preventing overtightening of the strap. The tension level may be regulated by controlling the volume flow rate or the pressure of the supply air. Otherwise, the operator may depress sealer lever 11 at a desired moment, to seel the strap 8 and cut off a section from the strap feeding supply. Depressing the sealer lever 11 disengages the tension motor/gear housing assembly 14, and engages the sealer valve 15 and the sealer motor 4. The sealer motor 4 drives the sealer cam 6 through the gearbox 5, rotating the sealer cam 6 one revolution. The surfaces on the sealer cam 6 act upon the elements in the sealer follower module, punching interlocking slits through sections of the strap 8, sealing the strap, and then cutting the sealed strap loose from the strap supply. An improvement over the prior art involves the means for terminating the sealing step. Referring to Figure 3, 4 and 5, a compact and reliable structure is disclosed for terminating the sealing step, and reducing the size and weight of the strapping tool. Figure 3 shows the strapping tool in the sealing mode. A release cam 13 is disposed on an end of the sealer cam 6 distal the gearbox 5. The direction of rotation is shown in Figure 3. Here, the sealer lever 11 has been depressed in the direction shown by the arrow, and has returned to a rest position. The sealer valve 15 has been moved up into the ON position by the movement of the sealer lever 11, thereby activating the sealer motor 4 and associated apparatus. A pawl 17, being biased in one direction, the bias in this embodiment shown to be counterclockwise, rotates to present a sealer valve support surface 20 to a portion of the sealer valve 15, which may be biased downward by a spring force. The sealer valve support surface 20 holds the sealer valve 15 in the ON position. Figure 4 shows the strapping tool 1 in the non-sealing mode. The release cam 13 has at this point in time rotated to present a release cam tooth 19 to the pawl 17. Specifically, the release cam tooth 19 acts against a release tooth surface 18, rotating the pawl 17 against its bias, and removing the sealer valve support surface 20 from contact with the sealer valve 15. This causes the sealer valve 15 to move in the direction of its spring bias to a closed position, to await the next sealing cycle. The direction of bias of the various elements may vary, depending on the specific embodiment, and the invention is therefore not limited to the specific embodiment shown in the schematic Figures 3 and 4. Figure 5 shows one embodiment of the pawl 17, including the sealer support surface 20 and the release tooth surface 18. In one embodiment, the tension lever 12 is held in the ON position by the tension shut off switch 10, which is biased to hold the tension lever 12 in the ON position. When the sealing lever 11 is activated, it releases the tension shut-off switch from its biased position against the tension lever 12, allowing the tension lever 12 to return to the OFF position. Also, the tension shut-off switch 10 may be manually released at any time during tensioning to terminate the tensioning of the strap. The present invention, through the new design of the combined sealing motor/valve module, and the new means for terminating the sealing step, addresses and solves the problem of providing a compact, reliable, lightweight hand-held strapping tool.

Claims: A compact hand-operated pneumatic strapping tool (1) having strap tensioning means (9) ; sealer means (7) for punching interlocking slits through overlapping strap sections, the sealer means (7) being driven by a pneumatically operated cam shaft (6); a valve module (3), the valve module (3) having a sealer valve (15) and a tension valve (16), the sealer valve (15) controlling a sealer motor (4), the tension valve (16) controlling a tension motor (14); and sealer disengagement means for terminating a sealing step after a complete cycle, and having a release cam (13) driven by the cam shaft; so that when a strap (8) is tensioned by the strap tensioning means (9), and sealed by the engagement of interlocking slots punched into overlapping sections of the strap (8), the sealing step is terminated by the action of the release cam (13); characterised in that the sealer disengagement means has a pawl (17), the pawl (17) having a release tooth surface (18) and a sealer valve support surface (20), and the release cam (13) has a release cam tooth (19) which acts against the release tooth surface (18) to rotate the pawl (17) in a manner which moves the sealer valve (15) from the ON to the OFF position, causing termination of the sealing step. A compact hand-operated pneumatic strapping tool according to Claim 1, in which the pawl (17) is biased to support the sealer valve (15) against the sealer valve support surface in the ON position, the sealer valve (15) being biased to move into the OFF position, wherein rotation of the pawl (17) by the release cam tooth (19) allows the sealer valve (15) to move off of the sealer valve support surface (20) and then move to the OFF position. A compact hand-operated pneumatic strapping tool according to claim 1 or claim 2, further comprising a tension lever (12), a sealer lever (11), and a tension shut-off switch (10), the tension lever (12) acting against the tension valve (16) to control the tension motor (14), the sealer lever (11) acting against the sealer valve (15) to control the sealer motor (4), the tension shut-off switch (10) is normally biased to hold the tension lever (12) in the ON position, the sealer lever (11), when moved to the ON position, acting to disengage the tension shut-off switch (10) from engagement with the tension lever (12), wherein the tension lever (12) moves to the OFF position, terminating the tensioning step. A compact hand-operated pneumatic strapping tool according to claim 3, wherein the sealer valve (15), and the tension valve (16) are contained in a compact valve module(2), the valve module (2) and sealer motor (4) being disposed adjacent one another along a top area of the strapping tool (1) substantially parallel to the sealer cam (6), a gearbox (5) is disposed in a generally vertical position at an end distant from the valve module (2), wherein the components are arranged to minimize the size of the strapping tool.

Inventors: CRITTENDEN DAVID, CRITTENDEN, DAVID
Applicants: ILLINOIS TOOL WORKS, ILLINOIS TOOL WORKS INC.
Application year: 1996
Main classification: B65B13
IPC codes: B25B25, B65B13