US3125326A - ericsson - Google Patents

Description

March 17, 1964 A. l. ERICSSON STRAPPING MACHINE 3 Sheets-Sheet 1 Filed July 19, 1960 March 1964 A. 1. ERICSSON STRAPPING MACHINE 3 Sheets-Sheet 2 Filed July 19, 1960 Inga;

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March 17, 1964 A. l. ERICSSON 3,125,326

STRAPPING mourns Filed July 19. 1960 3 Sheets-Sheet 3 United States Patent 3,125,326 STRAPPING MACHINE Arvid I. Ericsson, Chicago, Ill., assignor to Signode Steel Strapping Company, a corporation of Delaware Filed July 19, 1960, Ser. No. 43,826 1 Claim. (Cl. 25451) This invention relates to a strapping or ligature tying machine and, more particularly, to a novel, electrically powered strap tensioning mechanism for a strapping machine.

As illustrated and described in U.S. Patent 2,594,397 issued April 29, 1952 to the applicant hereof, as a coinventor, strapping machines of the type upon which the mechanism of this invention has particular application, generally have a flat-bottomed [frame member to which is attached one or more strap grippers, a strap tensioning mechanism, a strap sealer and a shear or cut-off device.

[Such machines are used by placing the flat bottom or package engaging surface of the machine upon the article being banded after the article has been enclosed with a loop of steel strapping. The tree end of the steel band or strap is inserted into a strap gripper on the machine. It may consist of a set of opposing knurled plates which bear against the strap located thereinbetween to grip it. The supply end of the strap, that is, that portion which has not been severed irom the supply roll and is in juxtaposition to the free end, is then inserted into the machine and engaged by the strap tensioner. This generally consists or" a mechanism in which a knurled wheel mounted for swinging movement downward toward engagement of the strap between the wheel and a lower member which may simply be knurled or may be just a wear plate.

Upon insertion of the strap into position, the upper wheel is swung downwardly to force the strap against the lower gripper or wear plate. The teeth of the wheel then bite into the strap. Repeated stroking oi a manually operated handle geared to the toothed wheel or actuation of a pneumatic drive, rotates the wheel to tighten or tension the loop of strap around the article. When the desired tightness or tension is reached, the sealer is actueted to place a seal around the juxtaposed portions of the strap and to crimp the same thereby sealing the strap together. The excess strapping leading to the supply roll is cut on its untensioned side or" the seal immediately after crimping. The machine is then slid laterally to remove it from the strapped article.

It has now been found that the above described machine can be improved by incorporating therein a novel electrically powered strap tensioning mechanism.

The strap tensioning mechanism of this invention uniquely permits use of an electrical motor to power the strap engaging or strap gripping wheel to continuously tension the strap to a predetermined level which is maintained until the strap is sealed and out. No burn-out oi the motor due to excess loading occurs. More particularly, the strap tensiouing mechanism of this invention consists of an electrical motor which operates a planetary gear assembly capable, by reason of an attached braking mechanism, of exerting an adjustable predetermined tensioning [force through the strap gripping wheel upon the strap while at the same time absorbing any excess force to prevent motor burn-out.

Alternatively, the machine may be powered by motors other than of the electrical type and the brake mechanism utilized as a tension adjusting means.

The mechanism of this invention and its application to strapping machines customarily encountered in the trade is more aptly described by reference to the accompaning drawings, in which:

FIGURE 1 is a side elevational view of a standard strapping machine into which the continuous power strap "ice tensiioning mechanism of this invention has been incorporate l FIG. 2 is a broken cross-sectional view of the tensioning mechanism;

FIG. 3 is a cross-sectional view of the tensioning mechanism shown in FIGURE 2, taken along line 3-3;

FIG. 4 is a cross-sectional View of the tensioning mechanism shown in FIGURE 2, taken along line 44;

FIG. 5 is a cross-sectional view of the tensioning mechanism shown in FIGURE 2, taken along line 5-5.

The strap tens-ioning mechanism *1 of this invention is shown in FIGURE 1 as being incorporated into a strapping machine 2 which is of customary design encountered in the trade. The strapping machine shown is described in great detail in US. Patent 2,594,397, cited above.

Although reference is made throughout description to the particular strapping machine shown, it should be realized that the mechanism of this invention can be incorporated into strapping machines of other design.

Briefly, the strapping machine 2, shown in FIGURE 1, consists of frame 5 with a flat base 6 which in use rests upon the package being bound.

The free end 8 of strap S is engaged and held against movement by strap gripper 1-1 which comprises two opposing knurled surf-aces which, in use, bear against each other or against the strap held thereinbetween.

The supply end 12 of strap S, alter it has been looped around the package is engaged by strap gripper and tensioner 13. It is so constructed that strap gripping wheel 14 bears down on the strap S to force it into engagement with wear plate 17. Rotation of the gripping wheel takes up the slack in the loop and tensions it tightly about the package.

After being tensioned, a seal from magazine 18 is placed around the juxtaposed portions of the strap and strap sealer 19 is actuated by handle 20 to close and crimp said seal around the strap. A cutter 23 shears the supply end of the strap from the bound paclcage.

The power strap tensioning mechanism 1, with which the invention is particularly concerned, is affixed to strapping machine 2 as a replacement for the manually operated tensioning mechanism heretofore used. The power mechanism, as seen best in FIGURE 2, consists of an electrical motor 24, housed within a motor housing 25. Alternatively, a pneumatic motor or a hydraulic motor may be utilized although the invention has more advantageous application when an electrical motor is utilized.

Extending forwardly (toward the right in the drawing) from the motor is a power shaft 26 journaled within ball bearing 28 which is housed within the rear portion (toward the left in FIG. 2) of upper gear housing 29. The term upper refers to the position of the housing when affixed to the strapping machine (see FIG. 1). Keyed to power shaft 26 is .a fan blade 39 which cools motor 24 during operation.

'I he speed of the motor is regulated by an appropriately geared speed reducer. Obviously, other speed control mechanisms are operable. In fact, it may be possible to completely eliminate the use of a speed controller in certain instances. The speed reducer shown consists of a first pinion gear 31, either keyed to or formed as an integral part of shaft 26. Gear 31 is intermeshed with and drives a first spur gear 34- located in the lower portion of the cavity within the upper gear housing 29. First spur gear 34 is keyed, or afiixed in an equivalent manner, to aide 35 which is disposed parallel to but removed from the main axis of the power mechanism. Axle 35 is journaled within ball bearings 3'6 and 37. Ball bearing 36 is housed within upper gear housing 29 while ball bearing 37 is housed within lower gear housing 49. To prevent end-wise movement of axle 35, transverse pin 40, ring 41 and shoulder 42 ot a second pinion gear 43 are utilized. Second pinion gear -'43 is either a separate gear member keyed to axle or is formed as an integral part of said axle. Pinion gear 43 engages second spur gear 46 which is keyed or integrally afiixed in an equivalent [fashion to shaft 47. Shaft 47 is journaled, at its rear end within bearing 48 housed in lower gear housing 49, land :at its front end within bearing 52 which is located within a rearwardly facing axial cavity 53 in worm 54. The several pinion and spur gears referred to above cooperate, by reason of their gear ratios, to regulate the rotational speed imparted to the braked planetary gear assembly discussed immediately below.

Afiixed to the intermediate portion of shaft 47 is a sun gear 55 which engages two planetary gears 58 and 59 (shown best in FIG. 5) which, in turn, engage a pcripherally located ring gear 60. The several movements of said planetary gears are described in more detail hereinarfter.

Each planetary gear 58 and 59 is rotatably mounted on studs 63 and 64 respectively. These studs extend rearwardly from a spider 65 affixed to the rear end of worm 54. Worm 54 is journaled near its rear section within ball bearing 66 and at its forward end within needle bearing 67. The needle bearing 67 is held, in typical fashion, within the front or lower cavity 89 of planetary gear and worm housing 68 by bearing sleeve 90, O-ring 91, threaded cap 9 2 and transverse pin 93.

A split ring 72 bearing against shoulder 73 on the body of worm 54 is used to control axial movement of the worm 54 relative to bearing 66.

Although not shown, provision for brass bushings between the studs 63 and 64 and the axial orifices of planetary gears 58 and 59 may be made to reduce wear and fniction between the two parts.

Washer 74 is located just rearwardly of the planetary gear assembly. Supported by shoulder 75 of the lower gear housing 49, it acts to contain the planetary gear assembly and the worm assembly within planetary gear and worm housing 68.

Engaging the outer peripheral surface of ring gear 60 is a split friction brake band or friction clutch 76, the inner diameter of which is adjustable by tension adjusting screw assembly 77 described in detail below.

The tension adjusting screw assembly 77 shown in detail in FIGURE 5 consists of a T-shaped cylindrical plunger 78 which bears against a flat 79 on split friction band 76. Spring 80 biases the plunger 78 against the flat 79.

Spring 80 and plunger 78 are located within well 83 which is tangential to planetary gear and worm housing 68. Tension exerted by spring 80 and plunger 78 is adjustable by simple rotation of either capscrew knob 84 or spring housing tube 85 threaded telescopically at its lower end into well 83.

The split friction band 76 is anchored to the planetary gear housing 57 by set screw 86.

The several housings; namely, motor housing 25, upper gear housing 29, lower gear housing 49 and planetary gear and worm housing 68 are held together by bolt 96 and alignment pins 97. Worm 54 is geared to worm gear 98. Gear 98 is directly connected to and powers strap gripping wheel '14. A cover plate 99 fastened by bolts 100 to the planetary gear and worm housing 67 covers the worm rack.

'If desired, gaskets (not shown) may be used between one or more of the several housings or between the worm housing and the worm rack cover plate 99 to provide a leakproof seal between them. Generally, a gearing oil is inserted into the speed reducer and worm cavities to insure a smooth, well lubricated, quiet operation of the parts therein.

The strap tensioning mechanism described is pivotally mounted to the strapping machine 2 by bolt 102.

A detent plunge-r 103 spring loaded by spring 104 bears against a flat 105 on the strapping machine 2' (see FIG.

5). Dctent plunger 1% has a mushroom head 107 which bears upon washer 108. The tip of the detent is normally located in a detent hole 106 to position the strap tensioning mechanism 1 and the strap gripping wheel 14 away from the wear plate 17. This permits insertion of strapping S. After the strapping is inserted into the space between the gripping wheel 14 and the wear plate 17, the machine 2 is pivoted upward (or counter-clockwise in FIG. 1) to engage wheel 14 against the strap.

An electrical switch 109 and electrical current supply means 110 are affixed to the strap tensioning device 2 to permit intermittent supply of electrical current to the motor.

As brieflly discussed above, machines of the type described are generally used by placing them upon the article being banded, after the latter has been enclosed by a loop of steel strapping. The operator generally stands facing the machine in the direction shown by Arrow OP in FIGURE 1. The free end of the strap is then placed into strap gripper 11 and the supply end is inserted into strap gripper and tensioner 13. The strap tensioning mechanism is then pulled counter-clockwise toward the operator to release detent 1.63 from detent hole 106 and to cause strap gripping wheel 14 to bear against strap S. The operator then closes switch .109 and power is supplied to motor 24. The gear ratio of the speed reducing gear train acts to control the rotational speed imparted to sun gear 55. Planetary gears 53 and 59 initially rotate around the sun gear in a spinning planetary fashion.

Studs 63 and 64 act as the spin axis for these planetary gears. Since the studs are directly connected to spider 65, the spider rotates about its own axis. The spider, in turn, rotates the worm 54. Since the worm 54 is geared to worm gear 98 which, in turn, is operatively connected to the strap gripping wheel 14, wheel 14 rotates. The loose strapping, engaged by wheel 14, is thereby eventually tensioned about the package. When the strapping is tensioned to -a force greater than that needed to overcome the brake action or friction existing between ring gear 60 and friction band 76, the planetary gears 58 and 59 stop rotating about sun gear 55 and merely spin about the studs 63 and 64. Thus, the spider and the Worm cease to rotate. The spinning of the planetary gears without rotation about the sun gear forces ring gear 60 to rotate about the axis of the assembly. In effect, the ring gearfriction brake band assembly is actuated at this stage to absorb the excess power generated by motor 24. Because of such absorption, without stopping the rotational movement of motor 2 4, the motor does not burn out. It might be here noted that the provision for adjustment of the amount of friction or slippage between the ring gear and the friction band provides an excellent control mechanism for effecting continuous tension of a predetermined amount. The adjusting mechanism regulates the amount of frictional force needed to cause slippage of the ring gear-friction band assembly. Only after such force is reached will slippage occur. Thus, a continuous tensioning force is imparted to the planetary gears and, hence, on the strap, so long as power is supplied. In effect, manual and pneumatic tensioning is duplicated and, in addition, an automatic control is exerted over the amount of tension applied to the strap.

After the strap S has been tensioned around the package, the strap seal applying and seal means and cutoff are activated. This involves the pulling of handle 20 towards the operator. With such movement, the machine cuts the strap, places a seal on the juxtaposed portions of strap, bends the seal around the strap and crimps it. The switch 109 of the strapping machine is then opened to stop the flow of current to the motor. The machine is then removed from the package.

The resultant package is found to be tightly bound by a closed loop of strap. Tension within the strap is found to be comparative in amount with similarly strapped packages using the same strapping machine under the same tension adjustment.

While a detailed description of the invention with particular reference to its application on one type of strapping machine has been provided, it is realized that certain modifications of the invention and adaptations to other ligature-tying-maohines may be made without departing from the spirit and scope of this invention. Such obvious modifications and adaptations are to be considered within the scope of this invention.

I claim:

A strapping machine comprising a frame member with a bundle-engaging surface thereon, strap gripping means and a wear plate carried by said frame member, a strap tensioning wheel movable between a strap-receiving position spaced from said wear plate and a strap-tensioning position adjacent said wear plate, and electrically powered means for rotating said tensioning wheel to cause the same to tension a strap around a bundle and maintain the tension which is applied until the strap is sealed, said electrically powered means comprising an electric motor adapted to supply continuous rotary power, a shaft-mounted spider including gear means operated by said shaft for rotating said tensioning wheel in one direction and means for directing the power supplied by said electric motor comprising a sun gear driven by said electric motor, planetary gears rotatably mounted on said spider and intermeshed with said sun gear, a ring gear encircling said planetary gears and intermeshed therewith, split ring friction means encircling said ring gear and normally preventing rotation of said ring gear so that said sun gear rotates said planetary gears to cause said planetary gears to revolve around said sun gear to rotate said spider, means for adjusting the tension on said split ring to limit the strap-tensioning force which can be applied to said shaft by said planetary gears before rotation of said planetary gears results in sliding movement of said ring gear within said split ring to cause rotation of said spider to substantially cease, excess power being bled ofi by rotation of said ring gear within said split ring, whereby operation of said electric motor will cause a strap to be tensioned to a predetermined degree and maintained under such tension while said electric motor operates continuously and with out overloading.

References Cited in the file of this patent UNITED STATES PATENTS 2,111,1 15 Gibbs et al Mar. 15, 1938 2,517,875 Henry Aug. 8, 1950 2,649,817 La Voque Aug. 25, 1953 2,791,920 Ray May 14, 1957 2,919,894 Helper Ian. 5, 1960 2,929,608 Zippel Mar. 22, 1960 2,941,782 Winkler June 2 1, 1960

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