Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF T~IE INVENTION
1. Field of the Invention
This invention relates to an apparatus for tiqhtening
a loop around an object comprising a first gripping jaw which
can be driven back and forth for a working stroke acting in the
tightening direction and for a return stroke, which gripping jaw
interacts with a counter jaw which is stationary in relation to
the gripping jaw. The purpose oE these jaws is to pick up
between them at least the one end region of a band loop to be
tightened. In order to execute the tightening operation in a
shorter time without a non-return lock being necessary, the
first gripping jaw is utilized with a second gripping jaw which
can be driven in the same direction as the first gripping jaw,
but in countercycle thereto and which likewise interacts with a
stationary counter jaw.
2. The Prior Art ~ -~
An apparatus of this type is known, for example, from
DE-C-2,709,322 (and the corresponding U.S. Patent No. 4,096,019)
or also from DE-A-2,521,474 (and the corresponding U.S. Patent
No. 3,984,278).
In these known apparati, the gripping jaw, which can
be driven in a working stroke and a return stroke, is assigned
a non-return lock which ensures th~t the end region of the band
h
loop cannot be displaced again aga;nst tlle tightening direction
during the return stroke of the gr-;ppillg jaw. Ilowever, this
means that the tightening operation takes place in steps, i.e.,
in each case only during a working stroke of the gripping jaw,
while it rests, however, during the following return stroke.
Additionally, a tying device is known from DE~A-
3,714,893 (and the corresponding GB-~-2,209,374), which tying
device has a tightening apparatus for tightening the band tied
around an object. This tightenillg apparatus has a plurality of
gripping jaws attached to a rotating chain. There are, there-
fore, always several gripping jaws acting on one of the two ends
of the band lying one on top of the other, which gripping jaws
in each case come into action on the band successively in the
region of a deflectional wheel.
This means that the gripping jaws come into contact
with the band at first only in the region of their forward end
and only gradually act on the band completely. However, this
can lead to undesired damage to the band when contacting the
gripping jaws. Additionally, this tightening arrangement is of
complex construction.
, ,
, ~ .
,
SUMM~RY OF TIIE INV~NTION
_ _ _ .
An object of the present in~ention is to provide an
apparatus on a tying device which, in a space-saving and
comparatively simple constructi~n, is capable of applying a
greater tensile force to the band to be tied, with careful
handling of the band during tightening than is possible in the
devices of the prior art type.
Tl-e above object is accomplished in accordance with
the present invention by providing an apparatus on a tying
device for tightening a loop of a tying band made of plastic ~:
placed around an object to be tied, comprising a first gripping
jaw; means for driving said first gripping jaw back and forth ;~
for a working stroke acting in a tightening direction and for a
return stroke; a counter jaw for interacting with said first ~:
gripping jaw, said counter jaw arranged in a stationary manner ;:
in relation to the first gripping jaw; said first gripping jaw
and said counter jaw picking up at least one of the end regions .
of the loop between them and acting upon the end region in
frictional engagement; and a second gripping jaw which can be .
driven back and forth in the same direction as the first
gripping jaw, but in countercyc~e thereto and which, in turn, -
interacts with the counter jaw which is stationary in relation
to the second gripping jaw.
- 3 -
.,~ ,
7r~;= - , . .. .
Since neither Or the two ~r;pping jaws allows the end
regions of the band loop to run back against the tigh~ening
direction during their working stroke, and since the two
gripping jaws are driven in countercycle in relation to each
other, an actual non-return lock is not necessary. The tighten-
ing operation takes place continuously, i.e., not in steps,
which makes it possible to have a greater tensile stress in the
stressed band.
The two gripping jaws moved forwards and backwards in
countercycle can each be placed on the band essentially with
their entire effective surface facing the band and can be lifted
from the band, by which means the damage resulting therefrom can
be kept at a low level.
BRIEF DESCRIPTION OF T~E DRAWINGS
Other objects and features of the present invention
will become apparent from the following detailed description
considered in connection with the accompanying drawing which
discloses one embodiment of the present invention. It should be
understood, however, that the drawing is designed for the
purpose of illustration only and not as a definition of the
limits of the invention.
In the drawing wher.~;n si.m;.lar reference characters
denote similar elements throughout the several views:
FIG. 1 shows a tightening and welding device formed
as a hand-operated device for tightening and welding tying bands
made of plastic:
FIG. 2 shows a side view of the gear system used in
the de~ice according to FIG. l.; and
FIG. 3 shows a plan view in partial section of the
gear system used in the device according to FIG. 1.
DETAILED DESCRIPTION OF T~IE PREFERRED EMBODIMENT
The hand-operated device 10 illustrated only schemati-
cally in FIG. 1 for welding the ends of plastic bands has a
housing 11 illustrated only by its outline. Mounted so as to be
rotatable in the housing 11 is a shaft 12, on which an eccentric ~ .
13 is fixedly seated. Mounted so as to be rotatable on the
eccentric 13 is a two armed lever 14, having an end 14a which
appears at the bottom of FIG. 1. ~ first gripping jaw 15 is
attached to end 14a in an articulated manner by means of a pin -~
16. This gripping jaw 15 interacts with a fixed counter ~aw 17.
The other end 14b of the two armed lever 14 located opposite the .
gripping jaw 15 has a shoulder 18, on which the one end of a
~ .
~ ~ . '.
\ - -
compression spring l9 ;s su~pol-tr(l. ~rlle oth~r end of this
compression spring 19 is suppol~te(l 011 the end reglon 20a o~ a
second lever 20 appearing at the bottom in FIG. 1. A second
gripping jaw 21 is attached in an articulated manner to this end
20a by means of a pin 22.
This gripping jaw 21 likewise interacts with the
counter jaw 17 formed as an elongated rail. The second lever
20 is mounted so as to be rotatab]e on a further eccentric 23
which, in turn, is fixedly seated on a shaft 24. The eccentric
23 is formed in the same way as the eccentric 13, but it is
arranged in relation to the latter by belng offset by 180. The
shafts 12 and 24 are coupled together by an interlocking gear,
which will be explained in greater detail with reference to
FIGS. 2 and 3, so that they rotate at the same speed and
preferably in the same direction.
Arranged on the side of the counter jaw 17 is a slide
25. The slide 25 has at its end 25a appearing on the left an
elongated hole 26, through which a guide pin 27 extends, which
is fixed to the housing. The slide 25 extends beyond the length
of the counter jaw 17 and is hinged at 28 to an arm 29 of a
three armed hand lever 30 which can be swiveled about a pin 31
which is fixed to the housing. The slide 25 is provided with
two stops 32 and 33 which are each to be utilized with the
bottom end 20a and 14a of the levers 20 and 14, respectively.
- 6 -
If the hand lever 30 is swiveled counterclockwise, the stops 32
and 33 touch the bottom ends of the levers 20 and 1~, re-
spectively, and swivel them counterclockwise so that the
gripping jaws 21 and 15 are lifted from the counter jaw 17.
Thus, the illustrated device 10 is ready to pick up the two
overlapping end regions of a band loop (not shown) from the side
appearing closer to the observer between the gripping jaws 15
and 21 on one side and the counter jaw 17 on the other side.
Then the slide 25 is moved back into the starting
position illustrated, by which means the two gripping jaws 15
and 21 are pressed against the upper one of the introduced end
regions of the band loop by the effect of the spring 19.
For tightening the band, the two shafts 12 and 24 are
driven at the same speed in the direction of the arrow 34 as is
to be explained in greater detail with reference to FIGS. 2 and
3. The two gripping jaws 15 and 21 are driven back and forth in
countercycle via the two eccentrics 13 and 23 which are, as
mentioned~ offset by l~o~ in relation to each other. The one
gripping jaw 15 or 21 thereby executes a forward movement in the
direction of the arrow A, while the other gripping jaw 21 or 15
executes a return movement in the direction of the arrow B.
During its forward movement A, the gripping jaws 15 and 21 are
each engaged with the top end region of the band loop, which end
region is thus pulled from left to right in relation to the
~ ` . ~
bottom end region resting 011 tl~e counter jaw 17. In this
manner, the band loop (not illust~ated) is tightened around the
object (likewise not shown).
During the return movement in the direction of the
arrow B, the gripping jaws 15 and 21 are each lifted slightly
from the end of the band in order not to impair the tightening
operation executed by the other gripping jaw. The movements of
the gripping jaws 15 and 21 are thereby coordinated with one
another in such a way that, in each case, the gripping jaw
executing a forward movement comes into engagement with the end
of the band before the returning gripping jaw is lifted from the
end of the band.
With increasing band stress, the torque to be applied
by the shafts 12 and 24 or by the drive motor (not shown) also
increases. As soon as the band stress has reached a pre-
determined value, the two shafts 12 and 24 are halted in a
manner described infra. Since one of the gripping jaws 15 and 21
i6 certainly to be in engagement with the previously tightened
' end region of the band, this gripping jaw, which is now no
longer driven, acts as a non-return lock, and the welding
operation can begin.
; For this welding operation, the components described
below are used, which are, therefore, only explained briefly
- 8 -
,
,~ ;
~,
.,
because they do not form part of the apparatus for tightening
according to the invention.
The one arm 3sa of a bent lever 35 i6 likewise mounted
in a swivel manner about the pin 31. The one end of a link 37
is hinged to the same arm via a further pin 36. In its center,
the link 37 has an elongated hole 38, through which an eccentric
40 seated on a shaft 39 extends. ~ welding jaw 42 is hinged to
the bottom end of the link 37 via a pin 41. In the crown region
of the bent lever 35, there is a bore hole 43 which is penetrat-
ed with clearance by an eccentric 45 seated on a shaft 44. The
eccentric 45 acts on a bolt 46, the kottom end of which dis-
placeably penetrates the end of the other arm 35b of the bent
lever 35. The bolt 46 is surrounded by a compression spring 47,
the top end of which is supported on the bolt 46 and the bottom
end of which is supported on the other arm 35b of the bent lever
35. The eccentric 45 has a recess 48 on its periphery.
Provided on the side of the bent lever 35 facing away
from the observer is a lever 50 which can be swiveled about a
pin 49, which lever is pressed against the periphery of the
eccentr~c 45 by means of a tension spring 51. The lever is
provided with a tooth 52 fitting into the recess 48 in the
region of the contact point of the lever 50 on the eccentric 45.
A further lever 53, which is in drive connection with
~$ ~i
~ ~ -,... . ... .
the eccentric ~5, is mo~mted ;n a swive]ling manner about the
pin 31. ~ rotation of the eccentr;c ~5 effects a downward
swivel movement to this lever 53. ~ le latter thereby comes into
action on the top end 14b of the lever 1~ and presses the latter
downwards. This results in the gripping jaw 15 being lifted ~-
from the end of the band. ~t the same time, the other gripping
jaw 21 is pressed against the top end of the band via the spring
19, by which means said end o~ the band is secured against
running back.
The lever 53 is provided with an arm 54 which inter-
acts with a latch 55 which is connectecl to a blade h~lder 56.
The above-mentioned swivel movement of the lever 53 causes the
arm 54 to come out of engagement with the latch 55 and the blade
holder 56 together with the blade lleld in it to be lowered onto
the top section of the band.
When the deæired tension in the band loop has been
reached, as already mentioned, the shafts 12 and 24 of the ec-
centrics 13 and 23 are halted. At the same time, the eccentric
45 is driven in the direction of the arrow C, likewise, the
eccentric 40, in the direction of the arrow D. However, the
eccentric 45 is only rotated by 180, i.e., until the tooth 52
engages in the recess 48. By this means, the bolt 46 is moved
downwards and the compression spring 47 causes the bent lever 35
to execute a swivel movement counterclockwise. Thus, the link
-- 10 --
37 is also lowered t1ntil the weldinc3 jaw ~ rests Otl the top end
region of tlle ban~ loop with the pressl~re arising from the
compression spring 47. Since the eccentric 40 also rotates in
the elongated hole 38, the welding jaw 42 executes a back and
forth movement which continues until the two end regions of the
band loop are welded together by friction welding. By the
movement of the welding jaw 42, the blade is pulled against the
upper section of the band, which leads to a severing oE the
band. By lifting the hand lever 30 over its other arm 57, the
lever 50 is then pressed downwards, whereupon the tooth ~2 is
disengaged from the recess 48, and the eccentric 45 executes a
rotation opposite to the direction of the arrow C by 180 into
the illustrated starting position under the effect of a return
spring shown only in FIG. 2. Thus, the welding jaw 42 and also
the gripping jaw 21 are lifted. The device can then be removed
from the completed band loop.
With reference to the schematic FIGS. 2 and 3, a gear
system is explained below, by which the mode of action described
above can be achieved for the device according to FIG. 1.
A drive motor (not illustrated) with opposite direc-
tions of rotation drives a drive shaft 60 (FIG. 3), on which a
bevel wheel 61 is seated. The wheel 61 is engaged with a gear-
wheel 62 which is arranged coaxially in relation to the shaft
39. This gearwheel 62 is connected via a freewheel clutch 63 to
-- 11 --
1 9~ :
. ~ .
:
a gearwheel 64, which is mounted 50 as to be freely rotatable on
the shaft 39. The ~reewheel clut~h 63 is effective when the
driveshaft 60 is driven in the direction of the arrow E. The
qearwheel 64 meshes with a gearwheel 65 which is arranged so as
to be freely rotatable on the shaft 12. Connected fixedly in ~;1
terms of rotation to the gearwheel G5 is a further gearwheel 66,
which is likewise seated so as to be freely rotatable on the
shaft 12. The two gearwheels 65 and GG are preferably seated on
a common hub, which is mounted so as to be rotatable on the
shaft 12. The gearwheel 65 is engaged with a further gearwheel
67, which is seated fixedly in terms of rotation on a shaft 68
which bears a driver 69, which is likewise seated fixedly in
terms of rotation on the shaft 68. This driver 69 meshes with
two gearwheels 70 and 71 which are connected fixedly in terms of
rotation to the shafts 12 and 24, respectively, which, as
explained with reEerence to FIG. 1, are used to drive the
gripping jaws 15 and 21.
If the drive shaft 60 is then turned in the direction
of the arrow E to tighten the tying band, the gearwheel 64 is
rotated clockwise via the freewheel clutch 63. The rotation of
the gearwheel 64 is transmitted via the gearwheels 65, 66 and 67
to the driver 69, which likewise rotates clockwise. This driver
69 drives the two gearwheels 70 and 71 and, thus, the shafts 12
and 24 in the direction of the arrows 34, i.e., counter-
clockwise.
- 12 -
., .
When the desired band tension has been reached, as
already mentioned earlier, a changeover takes place to the
welding operation. The drive motor reverses its direction of
rotation, and the drive shaft 60 is then rotated in the direc-
tion of the arrow F. In this case, the freewheel clutch 63 is
switched off. One of the two gri.pping jaws 15 or 21, however,
remains in engagement with the tightened band as a result of
automatic locking and, thus, retains its tension. On rotation
of the drive shaft 60 in the di.rection of the arrow F, a
freewheel clutch 72, which is arranged between the gearwheel 62
and the shaft 39, then becomes operable n Seated on this shaft
39 now driven counterclockwise is a gearwheel 73 which is
rotated in the direction of the arrow D. This gearwheel 73
meshes with a further gearwheel 74 which is fixedly connected in
terms of rotation to the shaft 44 which, as already described,
bears the eccentric 45. The gearwheel 74 has a gap 75 in the
region of its peripheral gear teeth. This gap 75 (FIG. 2)
coincides with the gearwheel 73 after a rotation of 180 from a
stationary position. ~t this moment, the gearwheel 74 and,
thus, also the shaft 44, are halted, since no further drive
action can take place on the gearwheel 74 by the gearwheel 73.
During this clockwise rotation of the gearwheel 74, the return
spring 76, illustrated only diagrammatically in FIG. 2, is
tensioned.
- 13 -
~ s already mentiolle(l, ti~e eccentric 45 is seated on
the shaft 44, which eccentric is provided with a recess 48
which, after the mentioned rotation of 180, comes into inter-
action with a tooth 52 on the lever 50. As already explained
above, this rotation of the eccentric 45 results in the welding
jaw 42 then being pressed against the overlapping sections of
the band and being driven back all(l fortll via the eccentric ~0
which is seated on the shaft 39.
It is understood that the tightening apparatus
described with reference to a hand-operated device 10 can also
be used in a stationary tying machine. In this case, it is
possible, both in a hand-operated device and in a stationary
tying machine, for the welding apparatus to be constructed
differently from that shown in the drawings. For example, it
could be that the welding jaw is driven transversely in relation
to the longitudinal direction of the band. Instead of a
friction welding apparatus, a welding apparatus operating by
means of ultrasonics, for example, can also be provided.
To reduce the friction, it can be advantageous,
especially for the stationary tying machines, to construct the
counter jaw 17, as a plate, or as a moving band or as a roller
base.
While only a single embodiment of the present inven-
- 14 -
'~tP~
`~ ~
tion has been shown and described, .it is to be understood that
many changes and modifications may be made thereunto, without
departing from the spirit and scope of the invention as defined
in tbc ~ r~ded clai~
:,~,.. .
: '
- 15 - ~
O~, ., .. ,, , :
