Machine tools abstract
The present invention relates to a bar guide device for bar feeders
in machine tools. The device has a plurality of guiding units which
are longitudinally aligned. Each guiding unit has a pair of sprockets
which are rotatable and have polygonal peripheral grooves. The grooves
are constituted by semicylindrical recesses which have different
diameters and form, in the mutually opposite position, a guiding
channel for a bar to be fed toward the machine tool.
Machine tools claims
I claim:
1. A bar guide device for bar feeders in machine tools, comprising
a plurality of mutually aligned bar guiding units defining a longitudinal
extension of said bar guide device, each unit comprising at least
one pair of cooperating sprocket members rotatable about mutually
parallel axes arranged transverse to said longitudinal extension,
each of said sprocket members having: opposite spaced apart side
wall faces; peripheral rim formations disposed between said side
wall faces; and a respective axis of rotation extending along one
of said parallel axes; said peripheral rim formations comprising,
for each one of said sprocket members, a shaped groove having a
shaped surface extending around said respective axis of rotation,
said shaped groove having a plurality of successive directrices
lying in a common plane and a plurality of successive generatrices
extending transverse to said directrices for defining a plurality
of successive peripherally open recesses in said shaped surface
of said shaped groove, said successive directrices lying in said
common plane transverse to said respective axis of rotation and
being rectilinear and forming an angle with respect to each other
and surrounding said respective axis of rotation progressively at
a different distance from said respective axis of rotation thereby
to form a polygonal directrix line surrounding said respective axis
of rotation for defining said recesses at progressively different
distances from said respective axis of rotation,
each of said successive generatrices corresponding to a respective
directrix of said directrices for defining a respective peripherally
open concave recess and lying in a respective plane transverse to
said respective directrix,
said successive generatrices being comprised of different generatrices
for each respective directrix, at least one of said generatrices
being in the form of a flattened line portion extending inwards
from one of said side wall faces to an intermediate position between
said opposite side wall faces, said at least one generatrix having
an arcuated form extending transverse to said flattened line portion
thereby to define with a respective directrix a peripherally and
laterally open recess,
others of said generatrices having an arcuated peripherally open
and laterally closed shape, each generatrix to define with a respective
rectilinear directrix a peripherally open laterally closed concave
recess thereby to form in said shaped groove a plurality of peripherally
open laterally closed recesses of progressively different radii
and having lateral side walls laterally closing said concave recesses,
said pairs of cooperating sprocket members having said sprocket
members of each pair lying in a common central line plane and with
at least two of said peripheral rim formations thereof in substantially
tangential relationship to each other and angularly arranged with
respect to each other with selected recesses of one of said sprocket
members of said pair of sprocket members facing a selected corresponding
recess of another of said two sprocket members of said pairs of
sprocket members,
thereby, when upon adjusting angular rotation of said sprocket
members of said pairs of sprocket members said laterally open recess
of one of said sprocket members of said pairs of sprocket members
substantially tangentially faces a corresponding laterally open
recess of another of said sprocket members of said pairs of sprocket
members, a lateral opening is formed therebetween for the passage
and containment therein of a bar to be guided,
and thereby to guide said bar when upon a further selected adjusting
angular rotation of said sprocket members of said pairs of sprocket
members a selected peripherally open concave recess is shifted over
said bar to substantially tangentially face a corresponding peripherally
open concave recess of another of said sprocket members of said
pairs of sprocket members whereby to define a closed cavity of selected
size containing said bar in guiding relationship therewith when
said sprocket members are stationary,
the device further comprising sprocket position adjusting means
for selectively transmitting angular rotation to said sprocket members.
2. The device according to claim 1 wherein said means for selectively
transmitting angular rotation comprise rack means extending along
said longitudinal extension and wherein said rim formations of said
sprocket members of each pair of sprocket members comprise meshing
toothed rims, at least one of said sprocket members having further
a pinion formation meshing with said rack means controlling the
angular positioning of said sprockets.
3. The device according to claim 1 wherein said sprocket members
are rotatable about parallel shafts defining said parallel axes
and wherein each of said parallel shafts has an axial lubricating
channel terminating with one end thereof in an intermediate position
of said shaft and connected with another end thereof with a source
of lubricant, said shaft has a radial lubricating channel opening
with one end thereof into said axial lubricating channel and with
the other end thereof opening into the outside at a peripheral portion
of said shaft and wherein said sprocket members have radial lubricating
holes leading from said peripherally open recesses towards said
radial lubricating channel to thereby lubricate said peripherally
open recesses.
4. The device according to claim 11 characterized in that the
device is applied on a drum-type bar feeder.
5. The device according to claim 1 wherein said means for selectively
transmitting angular rotation to said sprocket members of said bar
guiding units comprise rack means extending along said longitudinal
extension and wherein
said rim formations of said sprocket members of each pair of sprocket
members comprise meshing toothed rims, at least one of said sprocket
members having further pinion formations meshing with said rack
means controlling the angular positioning of said sprockets,
the device further comprising elongated bar pusher means with coupling
elements arranged along said longitudinal extension and actuation
means for advance and return stroke movements of said pusher means
in an advance stroke direction and a return stroke direction respectively,
wherein said rim formations have said peripherally open and laterally
closed concave recesses and laterally open recesses providing passages
for inserting said coupling elements into said laterally open recesses,
said rack means having each at least one pawl pivoted thereon,
said pawl having abutment means for interacting with said coupling
element during advance stroke movement of said bar pusher means
to thereby cause through said rack means angular rotation of said
sprocket members from a reference angular position into a selected
angular position in which said laterally open recesses of said pairs
of sprocket members face each other to form said passages for said
coupling elements,
said pawl having further abutment means interacting with said coupling
element to cause through said rack means opposite angular rotation
of said sprocket members into said reference angular position during
a return stroke of said bar pusher means.
6. The device according to claim 5 having further longitudinally
extending stationary sliding surface means for said rack means and
wherein said pawl has pivot means in an intermediate position thereof
for pivotal connection with said rack means, a first arm extending
from said intermediate position in said return stroke direction,
said first arm having said abutment means thereof in the form of
two opposite abutment surfaces for cooperation with said coupling
element, said pawl further comprising a second arm extending from
said intermediate position in the advance stroke direction, said
second arm having a tooth slidable along said sliding surface means
and being spring biased to urge said tooth against said sliding
surface means, said sliding surface means having a notch therein
for stopping engagement with said tooth thereby determining an end
of advance stroke position of said rack means in which said rack
means cause said sprocket members to assume said selected angular
position, said two opposite abutment surfaces cooperating with said
coupling element to tilt said alternatively in opposite directions
when said coupling element engages alternatively said two opposite
abutment surfaces.
7. The device according to claim 5 further comprising jack means
and sliding surface means for said rack means and wherein said rack
means have a sliding block on which racks are formed,
said sliding block having a U-shaped cross-section with two parallel
walls externally provided with said racks, which mesh with said
pinion formations formed on said sprocket members, said two parallel
walls internally forming a guiding channel for said coupling element
of said bar pusher means,
said sliding blocks being actuatable along said sliding surface
means extending along said longitudinal extension, by means of said
jack means over such an extent that said racks rotate said sprocket
members of said bar guiding units between a loading position in
which said laterally open recesses face each other to form said
laterally open cavity, so as to allow the loading of the bar to
be machined, and a guiding position in which the peripherally open
and laterally closed recesses corresponding to the diameter of said
bar face each other so as to receive therein and guide said bar.
8. The device according to claim 7 wherein said jack means include
a second jack and a second actuation rod connected with one end
thereof to said second jack and extending along said longitudinal
extension, said sliding blocks each having a second longitudinal
hole through which said second actuation rod is driven, said bar
guiding units including a group of, from the direction of said second
jack, initial bar guiding units, said second actuation rod having
abutments engaging said sliding blocks of said initial guiding units
for transmitting translatory movement to said sliding blocks and
the racks thereof of said initial bar guiding units when said second
jack is actuated to thereby rotate said sprocket members of said
initial bar guiding units through said sliding blocks and rack means
thereof into a position for inserting therein said bar pusher means.
9. The device according to claim 7 wherein said jack means include
a first jack and a first actuation rod connected with one end thereof
to said first jack and extending along said longitudinal extension,
said sliding blocks having each a first longitudinal hole through
which said first actuation rod is driven, said first actuation rod
having abutments engaging said sliding blocks for transmitting translatory
movement to said sliding blocks and the racks thereof when said
first jack is actuated to thereby rotate said sprocket members between
said loading position and said bar guiding position, said first
actuation rod having spring means mounted thereon for maintaining
in engagement said abutments thereof with said sliding blocks.
10. The device according to claim 9 further comprising selectively
operable stroke limiters for determining selected end of stroke
positions of said actuation rod and said rack means in engagement
with said abutments of said rod, thereby to cause said sprocket
members of said pairs of sprocket members to assume corresponding
selected angular positions.
11. A sprocket structure for bar guide devices, comprising an axis
of rotation, opposite spaced apart side wall faces, peripheral rim
formations disposed between said side wall faces, at least one of
said peripheral rim formations being a toothed rim, another of said
peripheral rim formations being in the form of a shaped groove having
a shaped surface extending around said respective axis of rotation,
said shaped groove having a plurality of successive directrices
lying in a common plane and a plurality of successive generatrices
extending transverse to said directrices for defining a plurality
of successive peripherally open recesses in said shaped surface
of said shaped groove, said successive directrices lying in said
common plane transverse to said axis of rotation and being rectilinear
and forming an angle with respect to each other and surrounding
said axis of rotation progressively at a different distance from
said axis of rotation thereby to form a polygonal directrix line
surrounding said axis of rotation for defining said recesses at
progressively different distances from said axis of rotation, each
of said successive generatrices corresponding to a respective directrix
of said directrices for defining a respective peripherally open
concave recess and lying in a respective plane transverse to said
respective directrix,
said successive generatrices being comprised of different generatrices
for each respective directrix, at least one of said generatrices
being in the form of a flattened line portion extending inwards
from one of said side wall faces to an intermediate position between
said opposite side wall faces, said at least one generatrix having
an arcuated form extending transverse to said flattened line portion
thereby to define with a respective directrix a peripherally and
laterally open recess,
others of said generatrices having an arcuated peripherally open
and laterally closed shape, each generatrix to define with a respective
rectilinear directrix a peripherally open laterally closed concave
recess thereby to form in said shaped groove a plurality of peripherally
open laterally closed recesses of progressively different radii
and having lateral side walls laterally closing said concave recesses.
12. A bar guide device for bar feeders in machine tools, comprising
a plurality of mutually aligned bar guiding units defining a longitudinal
extension of said bar guide device, each unit of said guiding units
comprising at least one pair of cooperating sprocket members rotatable
about mutually parallel axes arranged transverse to said longitudinal
extension, each sprocket member of said pair of sprocket members
comprising a plurality of peripherally open recesses, each recess
of said plurality of recesses having an axis which is transverse
to an axis of rotation of said sprocket member and which is spaced
a distance away from said axis of rotation, said distance progressively
increasing for successive recesses of the sprocket member and said
sprocket members cooperating upon rotation thereof to form a plurality
of mutually different sized channels for accommodating a bar to
be fed.
13. The device of claim 12 wherein one channel of said plurality
of channels when formed is open laterally and comprises flattened
portions, and wherein remaining channels of said plurality of channels
when formed are essentially completely closed with a circular cross
section.
Machine tools description
BACKGROUND OF THE INVENTION
The present invention relates to a bar guide device for bar feeders
in machine tools.
As is known, in the field of machining it is necessary to guide
a bar both along its advancement direction and in its rotation.
Advancement requires the forming of a longitudinal slot to allow
the passage of the element for coupling the bar pusher to the transfer
train.
When the diameter of the bar varies, there is also the problem
of changing the dimensions of the channel in which the bars are
guided in order to avoid excessive play which might cause vibrations
of the bars.
SUMMARY OF THE INVENTION
An aim of the present invention is to provide a device which can
be adapted rapidly and safely so as to guide, within the tolerance
plays, bars having different diameters. This aim is achieved with
a device according to claims 1-2.
Within the scope of this-aim, an object of the present invention
is to provide a device allowing the advancement of the bar pusher
without requiring a continuous slot for the passage of the element
for coupling the bar pusher to the transfer train.
This object is achieved with a device according to claims 3-10.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features of the present invention will become apparent
from the following description on the basis of the accompanying
drawings, wherein:
FIG. 1 is a perspective view of the device in the position for
receiving a bar;
FIG. 2 is a perspective view of the device with a bar in a guiding
position;
FIG. 3 is a sectional view of the sprockets in the bar receiving
position;
FIG. 4 is a sectional view of the sprockets in the bar guiding
position;
FIGS. 5 and 6 are sectional views taken along the planes V--V and
VI--VI of FIGS. 3 and 4;
FIG. 7 is a side view of a different embodiment of the device;
FIG. 8 is a plan view;
FIGS. 9 and 10 are enlarged-scale side views of a detail of the
device in two operating conditions;
FIG. 11 is a transverse sectional view, taken along the plane XI--XI
of FIG. 7;
FIG. 12 is a plan view of a unit with a sprocket shown in cross-section
as taken along the plane XII--XII of FIG. 11;
FIG. 13 is a transverse sectional view of an embodiment which provides
for a plurality of guiding devices arranged angularly around a central
longitudinal axis.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to the above figures, the device is generally designated
by the reference numeral 1 and comprises a plurality of guiding
units 2 distributed longitudinally.
Each guiding unit 2 is constituted by a pair of sprockets 3 and
4 which are rotatably supported by respective parallel shafts 5
and 6 protruding from a stationary supporting framework (not shown
in the drawing), which is constituted for example by a central shaft,
such as the shaft designated by the reference numeral 106 in the
embodiment of FIG. 13.
The sprockets 3 and 4 have opposite side wall faces 3a, 3b and
4a, 4b; comprise portions 7 and 8 which constitute constantly mutually
meshing gears having on one side a cylindrical tang 9 and a toothed
pinion 10 respectively.
A rack 11 is guided between the pinion 10 and the tang 9 meshes
with the pinion 10 and has its back in tangential contact with the
tang 9. The sprockets 3 and 4 have, at the opposite end with respect
to the gears 7 and 8 collars or rime 7a and 8a having a diameter
smaller than the mutual distance of their axes, thus forming a slot
through which the element for coupling the bar pusher to the transfer
train can pass.
A polygonal groove is formed in the peripheral region of the sprocket
3 and comprises a plurality of peripherally open recesses 12 13
14 15 and 16 which constitute the sides of the polygonal groove
and are distributed at identical angles around the shaft 5.
The recesses 13-16 have a concone semicylindrical shape and their
axes or dirictrices are at right angles to the axis of the shaft
5 and are all arranged on the same plane. The diameter of the generatrices
of the recesses 13-16 furthermore increases from the recess 13 to
the recess 16. In other words the recesses 13-16 are delimited by
respective surface portions generated by respective semicircular
generatices of different diameters of which the generatices 14',
15' and 16' are visible in FIGS. 3 and 4. The directrices of the
respective surface portions of the recesses 12-16 are rectilinear
lines 12", 13", 14", 15" and 16" visible
in FIGS. 5 and 6 all lying in a common plane and forming an angle
between each other and arranged at progressively different distances
from the axes of respective shafts 5 thereby forming a polygonal
directrix line. It should be noted that the recess 12 or its generatrix
12", differently from the others, is not concave or semicylindrical
that is to say is not semicircular i.e. laterally closed but is
laterally opened by a flattened or rectilinear portion 17 parallel
to the shaft 5 and cutting through the collar 7a. In fact, as visible
in FIG. 3 the generatrix 12' of the recess 12 is not semicircular
but it has a rectilinear portion 17' extending from an arcuating
portion 12a. The sprocket 4 also has a peripheral polygonal groove
comprising a plurality of identical recesses i.e. generatices and
directrices which are arranged symmetrically with respect to the
recesses 12-16 and respective generatrices and directrices; and
are designated by the same reference numerals.
The meshing of the gears 7 and 8 is chosen so that the recesses
12-16 of the sprocket 3 are arranged opposite to the respective
recesses 12-16 of the sprocket 4 during the rotation of the sprockets
3 and 4.
In this manner, channels or cavities 18 with a diameter corresponding
to the diameter of the oppositely arranged recesses are formed in
each instance. In particular, when the recesses 12 are oppositely
arranged between the sprockets 3 and 4 a laterally open channel
19 is formed which has walls constituted by the flattened portions
17 or generatrices 17'.
The operation of the described device will become apparent from
the observation of FIGS. 1 and 2.
In the operating position of FIG. 1 the racks 11 are actuated
so that the recesses 12 are mutually opposite so as to form the
channel 19 between the sprockets 3 and 4.
In this situation it is possible to insert in the channels 19 of
the various units 2 a bar 20 which must be fed toward a machine
tool by means of an appropriate bar pusher. When the bar 20 has
been inserted in the channels 19 of the guiding units 2 the rack
11 is actuated so that it rotates the sprockets 3 and 4 until the
channels whose diameter is slightly larger than that of the bar
20 close. In the drawing it has been assumed that said channels
are those defined by the recesses 16. Radial movements of the bar
are effectively prevented by means of the closure of the channels;
however, said bar remains guided longitudinally in order to be fed
toward the machine tool.
It should be noted that the difference in diameter between the
semicylindrical recesses 12-16 forms corners which, when appropriately
chamfered, act as ramps and allow the bar 20 inserted in the channel
19 to rise in the selected channel when the sprockets 3 and 4 are
rotated. As can be seen, a slot allowing the passage of the coupling
element of a bar pusher remains between the collars 7a and 8a. Said
slot does not allow to guide and feed small-diameter bars and is
the source of noise. The embodiment of FIGS. 7-13 is provided in
order to obviate these drawbacks.
In the embodiment of FIGS. 7-13 the device comprises a plurality
of guiding units 101 distributed longitudinally.
Each guiding unit 101 is constituted (see FIG. 11) by a pair of
sprockets 102 and 103 arranged symmetrically with respect to a longitudinal
centerline plane C and rotatably supported on respective parallel
shafts 104 and 105 which protrude from a base 106. Said base 106
is, for example (see FIG. 13), a prism-like drum rotatable about
a longitudinal central axis and on the faces of which various guiding
units, sized for guiding bars of various kinds, are arranged.
A peripheral groove 107 and 108 is formed in the sprockets 102
and 103 and delimits two toothed collars 109 110 and 111 112.
For convenience in description, the toothed collars 109 111 are
termed "upper collars", whereas the toothed collars 110
112 are termed "lower collars", with reference to the
face 113 of the base 106 on which they are arranged.
The grooves 107108 have a polygonal shape, since they comprise
a plurality of semicylindrical recesses 107a, 107b, 107c, 107d,
107e and 108a, 108b, 108c, 108d, 108e which have co-planar axes
or directrices at right angles to the shafts 104 and 105 and are
distributed around said shafts so as to form identical angles, between
said axes and directrices and so that the grooves 107 and 108 increase
in depth i.e. in diameter of the corresponding semicircular generatrices
along a circumferential direction.
The toothed collars or rims 109 111 and 110 112 mutually mesh
and are arrangeable so that a recess 107a-107e of one sprocket 102
is arranged opposite to a corresponding recess 108a-108e of the
sprocket 103 which has the same generatrix diameter, so as to circumscribe
a circular cavity or channel, the diameter whereof corresponds to
the diameter of the oppositely arranged recesses.
The deepest recesses 107a, 108a, differently from the other recesses,
are not semicylindrical but are laterally opened by chamfers 114
115 which are slightly flared toward the free ends of the shafts
104105 which affect the upper collars or rims 109 and 111. The
lower collars 110 112 furthermore have faces 114a, 115a parallel
to the recesses directrices of the 107a, 108a. As more clearly shown
by the plan view of FIG. 12 (in which the two sprockets are spaced
in a non-meshing position for the sake of clarity of the drawing),
the plane of the chamfers 114 115 is slightly inclined with respect
to the plane of the respective faces 114a, 115a and thus with respect
to the directrix of the recesses 107a, 108a. The upwardly i.e. laterally
with respect to the rims 109 111 open seats in which the bar to
be machined is insertable are delimited or formed in the angular
position of the sprockets in which the chamfers 114 115 are parallel
to the longitudinal centerline plane C. In this position the faces
114a, 115a and the recesses 107a, 108a converge in the bar advancement
direction A (see FIG. 12).
Between the lower collars 110 112 and the face 113 the sprockets
have pinions 117 118 having a smaller diameter than the collars
110 112.
Two respective racks 119 120 mesh with the pinions 117 118 and
are formed on the side walls of a sliding block 121 sliding in a
complementarily shaped slot 122 formed longitudinally in the face
113 of the base 106.
The sliding block 121 has a U-shaped cross-section, with two mutually
parallel walls 123 124 on the outer faces of which the racks 119
120 are formed; said walls laterally delimit a channel 125 and rise
from a plate 126. The plate 126 slides appropriately on a strip
127 arranged so that it covers the bottom of the slot 122.
Two longitudinal holes 128 129 are formed in the plate 126 laterally
to the channel 125. The holes 128 of the sliding blocks 121 are
aligned, and a rod 130 is driven through them; said rod is actuatable
in the direction A by a pneumatic or hydraulic jack 131 against
the biasing action of a return spring 132. Collars 133 are arranged
on the rod 130 and, when the jack 131actuates the rod 130 in the
direction A, act as actuation elements for the sliding blocks 121.
Springs 134 are arranged between the sliding blocks 121 and the
collars 133 downstream of said collars and keep the sliding blocks
121 in abutment against the collars located upstream. An abutment
130 a is provided at the end of the rod 130 and is suitable to interact
with a pin, chosen among a plurality of pins 130b, when the rod
130 is moved back by the spring 132 in a direction opposite to the
direction A once the action of the jack 131 has ended. Thus the
pins 130b cause the sliding blocks to stop at a point in which the
angular position of the sprockets produces the mutually opposite
arrangement of the recesses 107a-107e and 108a-108e which correspond
to the diameter of the bars to be machined.
A rod 135 is driven in the holes 129 of only some of the initial
units 101 and collars 136 are fixed on said rod along the portions
arranged between the units 101. The rod 135 is actuatable by means
of a jack 137 so that it moves the sliding blocks 121 in the same
direction A independently of the activation of the jack 131.
A plate-like pawl 139 is pivoted in each sliding block by means
of a pivot 138 and is accommodated in a seat 140 formed on the internal
face of the wall 123.
The pawl 139 (see FIG. 10) comprises an arm 141 provided with a
tooth 142 protruding through a slot 143 of the base plate 126 of
the sliding block 121. The pawl 139 is actuated against the bottom
plate 126 by a spring 144 so that in a given longitudinal position
of the sliding block 121 the tooth 142 can engage, through the slot
143 an opening 145 formed in the strip 127 at each guiding unit
101.
The pawl 139 has a second arm 146 protruding from the seat 140
and ending with a tab 147 in which a channel 148 is formed; said
channel 148 is Z-shaped, with two parallel and horizontal portions
joined by a vertical portion which forms two abutments constituted
by steps 149 and 150. A pin 151 engages the channel 148 and protrudes
from a rib 152 of a coupling element 153 of a pusher or rod 154
for the advancement of the bars (FIG. 8).
In order to allow the passage of the pin 151 and of the tab 147
below the sprocket 102 an angular portion 154a of the lower collar
110 has been removed. The coupling element 153 comprises a slider
155 guided in a U-shaped profiled element 156 extending along the
channels 125 of the sliding blocks 121. The slider 155 is connected,
by means of the rib 152 to a bush 157 from which the bar pusher
rod 154 protrudes. The diameter of the bush 157 is equal to the
maximum diameter formed by the mutually opposite arrangement of
the recesses 107a, 108a having the largest diameter. A passage 158
is formed in the slider 155 and is crossed by the two straight and
superimposed portions of a belt 159 for moving the bar pusher; the
upper portion of said belt is fixed to the slider.
The belt 159 runs within the profiled element 156 and is closed
in a loop around a plurality of guiding pulleys 160a, 160b, 160c
and 161a, 161b and a pulley 162 driven by a motor 163.
The operation of the described device is as follows.
Assume that one wishes to feed toward a machine tool bars having
a diameter equal to the opening which can be obtained by arranging
the recesses 107e, 108e of the sprockets having the smallest diameter
mutually opposite. For this purpose, the pin 130b is selected; by
virtue of the spring 132 said pin stops the abutment 130 a in the
position in which the recesses 107e, 108e are arranged mutually
opposite. In this position, the springs 134 keep the sliding blocks
121 in abutment against the collars 133.
Assuming that the bar pusher 154 is in retracted position, first
of all the bar is loaded between the sprockets of the guiding units.
For this purpose, the rod 130 is actuated, by means of the jack
131 in the direction A so that the collars 133 by acting on the
sliding blocks 121 produce the simultaneous sliding of all the
sliding blocks and thus the rotation of the sprockets into the position
in which the chamfers 114 115 are mutually opposite. As shown by
FIG. 12 the faces 114a, 115a form an acute angle in the direction
A.
Since the chamfers 114115 are mutually parallel in this position,
it is possible to insert a bar between them.
When the jack 131 is deactivated, the spring 132 returns the rod
130 into abutment against the pin 130b, thus stopping the sliding
blocks 121 in the point in which, by means of the rotation of the
sprockets 102 103 due to the racks 119120 the recesses 107e,
108e which allow the best guiding of the bar are mutually opposite.
It should be noted that the diameter of the recesses is the most
suitable among those available in order to guide the bar with the
smallest possible play and at the same time allow the advancement
of the bar pusher, which usually has a larger diameter than the
bar.
After loading has thus been completed and after the bar has been
positioned in the recesses 107e, 108e of the sprockets, the motor
163 is activated so that it causes the advancement of the bar pusher
154 through the guiding units, the sprockets of which are momentarily
orientated by the wedge-like action applied by the rib 152 in the
faces 114a, 115a so as to move mutually opposite the recesses 107a,
108a which have the largest diameters and form the passage channel
for the bush 157 of the bar pusher. As soon as this preliminary
angular positioning of the sprockets by the rib 152 has been completed,
the pin 151 of the coupling element 153 enters the channel 148 of
the pawl 139 and abuts against the step 149 (FIG. 9).
Since the pawl is prevented from rotating by the abutment of the
tooth 142 against the strip 127 the sliding block 121 is moved
in contrast with the action of the spring 134 and the sprockets
102 103 consequently rotate. When the tooth 142 reaches the opening
145 the thrust applied by the pin 151 combined with the thrust
of the spring 144 produces the engagement of the tooth 142 in the
opening 145 and the lifting of the tab 147 so that the pin 151
can disengage from the step 149 and protrude forward (FIG. 10).
Since the tooth 142 is kept in the opening 145 by the spring 144
and since in this position the slot 116 forms and the recesses 107a,
108a are mutually opposite, the coupling element 153 can continue
its stroke through the related guiding unit 101.
The above described operations are repeated for all the units crossed,
which remain all in "open" position at the end of the
advancement of the bar pusher.
The initial conditions are restored during the return stroke of
the bar pusher. During said return stroke, the pin 151 in fact enters
the channel 148 on the opposite side, so that it abuts on the step
150 causing the oscillation of the pawl 139 in the position in which
the springs 144 previously pressed by the advancement stroke of
the sliding blocks 121 keep the step 149 rested on the pin 151.
In this manner, during the return stroke of the bar pusher the
sliding blocks do not snap into the initial position but are sequentially
carried backward, following the movement of the belt 159.
The described device perfectly achieves the intended aim and objects.
In particular, it should be noted that the collars 109-112 by virtue
of the meshing of the sets of teeth, fully close the seats for the
passage of the bars, which accordingly are always perfectly guided.
A particularity of the present invention is that it allows to load
the bars from below in a drum feeder such as the drum feeder shown
in FIG. 13. In this case, the bar remains firmly retained within
the lower guiding units, but would fall if use of a new bar pusher
rod 154 which requires the temporary opening of the guiding channel
(i.e. the rotation of the sprockets 102 103 into a position in
which the recesses 107a, 108a are mutually opposite), is intended.
The described device obviates this by providing, by means of the
activation of the jack 137 and of the traction applied by the rod
135 on the sliding blocks 121 the opening only of the guiding units
allowing to apply the bar pusher rod, whereas the-other guiding
units maintain their closed position. According to a different embodiment
of the present invention, radial holes 24 164 (FIGS. 3 4 11
12 and 13) are formed in a median plane of each sprocket and lead
into the recesses 12-15 107b-107e and 108b-108e.
The radial holes 164 of each sprocket 102 103 are connectable
to a hole 165 formed radially in the sprocket rotation pivot 104105.
The holes 165 lead into holes 166 which extend axially in the pivots
104 105 and are connected to a source for the supply of lubricant.
In this manner, the sprockets act as lubricant distributors, since
they allow to deliver lubricant only into the recesses forming the
guiding channels of the bars. It should be noted that there are
no radial holes toward the recesses 107a, 108a in order to avoid
the leakage of lubricant when the guides are open. |