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Claims  |
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I claim:
1. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of said member against said adjustable force for
controlling said drive means, the actuating force acting on said gripper
being transmitted by said gripper to said member in the drive associated
with the first gripper movement causing said member to be displaced and
actuate said switch means to initiate a second gripper movement.
2. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of said member against said adjustable force for
controlling said drive means, said displaceable force transmitting member
is a worm and movement of said worm is damped by means of a
shock-absorber.
3. A handling device according to claim 2, wherein the shock-absorber
comprises a damping cylinder which extends parallel to the worm, and is
equipped at its ends with covers, the damping cylinder being in frictional
contact with the worm in the axial direction, while in the rotational
direction it is connected with the worm in a rotationally free manner, and
comprises furthermore a piston which is fixedly mounted inside the damping
cylinder and to which pressure can be admitted from either side, a
pressure pipe with a restricting zone leading into each of the pressure
chambers of the shock absorber.
4. A handling device according to claim 3, wherein the piston connects at
either end with a piston rod, the rods extending through the covers and
being supported in a stationary manner.
5. A handling device according to claim 3 wherein each of the two covers of
the damping cylinder comprises an annular extension which freely rotates
around the worm and rests with one of its axial ends against the bottom of
the sleeve.
6. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of said member against said adjustable force for
controlling said drive means, said gripper connecting with a swivel-base
so that it may perform a swivelling movement, a pivoted bolster being
fixed to said swivel-base and swivelling together with the swivel-base
around the swivel axis of the latter, and connected with a motor in a
rotatably fixed manner, said displaceable force transmitting member being
a bolster displaceable around a bolster shaft against said adjustable
force, said shaft extending parallel with said swivel axis and the drive
shaft of said motor which is coaxial with the bolster shaft being in
frictional contact with a driving gear wheel engaging with a fixed
bearing, whereby when said actuating force which acts upon the gripper is
smaller than said adjustable force, said driving gear wheel rolls on said
fixed bearing thereby swivelling both said pivoted bolster and said
swivel-base to which said gripper is fixed, while with an actuating force
greater than said adjustable force, both said driving gear wheel and said
driving shaft are stationary and said motor, together with said pivoted
bolster, rotates around said bolster shaft in a direction opposed to said
adjustable force, and said switch means being operated by said rotational
movement.
7. A handling device according to claim 6 wherein the fixed bearing
comprises a toothing.
8. A handling device according to claim 6 wherein the adjustable force is
induced into the pivoted bolster from two opposite directions, through two
piston rods, each of them being connected with a piston which is flexibly
supported in a corresponding cylinder fixed to the swivel-base.
9. A handling device according to claim 6 wherein the pivoted bolster
comprises a lug which projects in a direction perpendicular to the bolster
shaft, two switch-elements being correlated to said lug and connected with
the swivel-base, these switch elements being symmetrically arranged in
relation to a plane defined by the bolster axis and the swivel axis.
10. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of said member against said adjustable force for
controlling said drive means, said gripper connecting with a threaded nut
to provide a linear movement, said threaded nut having a bore extending
parallel to the direction of said linear movement and engaging with the
threaded portion of a spindle constituting said displaceable member and
which is axially displaceable against said adjustable force, said spindle
being rotatable by means of a driving gear wheel driven by a motor whereby
when said actuating force acting on said gripper is greater than said
adjustable force, said spindle is axially displaced against said
adjustable force, and said switch means being actuated together with said
spindle.
11. A handling device according to claim 10 wherein the driving gear wheel
engages with a driven gear wheel which is keyed on to a carrier sleeve
which is fixed in the axial direction and whose internal bore is connected
with the spindle in a rotatably fixed manner.
12. A handling device according to claim 10 including a force-element which
acts upon the spindle against the direction of the gravitational force,
i.e. in an upward direction, when the spindle is vertically arranged.
13. A handling device according to claim 12, wherein a second sleeve which
is in frictional contact with the spindle in the axial direction,
surrounds the spindle above the carrier sleeve, a spring resting against
the closed end of the sleeve, which is remote from the carrier sleeve, the
other end of the spring acting upon the axially fixed carrier sleeve.
14. A handling device according to claim 13 wherein the sleeve comprises at
least one lug which projects sideways and is correlated to a
switch-element.
15. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of said member against said adjustable force for
controlling said drive means, said gripper connecting with a driving gear
wheel driven by a motor to perform a linear movement, the drive shaft of
said gear wheel extending at right angles to the direction of the
movements of said gripper, and said gear wheel engaging with a toothed
rack constituting said displaceable force transmitting member and being
displaceable in a longitudinal direction against said adjustable force
whereby when said actuating force acting upon the gripper is greater than
said adjustable force, said toothed rack is displaced against said
adjustable force, said switch means being actuated together with said
toothed rack, and further comprising a piston rod with a piston located in
a fixed cylinder which acts upon the upper portion of said toothed rack in
a system where said toothed rack is mounted vertically.
16. A handling device according to claim 15, wherein pressure is admitted
from above to the piston while the gripper together with the parts which
are connected with it, moves rapidly downwards, that is to say when their
weight is small because of the forces of inertia which act in the opposite
direction, while no pressure is admitted to the piston when the gripper
including the parts which are connected with it, moves slowly downwards.
17. A handling device according to claim 15 wherein the toothed rack
comprises at least one lug which projects in a direction perpendicular to
its longitudinal axis and with which is associated a switch-element.
18. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of said member against said adjustable force for
controlling said drive means, said gripper comprising a number of jaws
which are flexibly supported thereon and capable of gripping components, a
piston in a cylinder bore and the gripper being associated with each of
said jaws whereby the individual jaws can be displaced when pressure is
admitted to the corresponding piston, at least one pair of said jaws
consisting of two jaws which are movable towards each other or away from
each other, and being supported on said gripper, said two jaws engaging
through a projection inside the gripper which engages with a recess in the
corresponding piston.
19. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of said member against said adjustable force for
controlling said drive means, said gripper comprising a number of jaws
fixedly supported thereon and capable of gripping components, a piston in
a cylinder bore and said gripper being associated with each of said jaws
whereby the individual jaws can be displaced when pressure is admitted to
the corresponding piston, each of said cylinder bores housing one of said
pistons connected with a respective jaw, the axial end sections being
remote relative to each other and belong to two cylinder bores
corresponding to a pair of jaws being interconnected through a connecting
line whereby said two jaws are caused to move towards each other when
pressure is admitted to one of said two end sections, the wall section
separating the cylinder bores corresponding to a pair of jaws including an
opening in which a gear wheel is pivoted engaging with the middle sections
of the two pistons which are designed as toothed racks.
20. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of the member against said adjustable force for
controlling said drive means, said switch means including two switch
elements associated with each of the displaceable members in the drives
for a given gripper movement, said switch elements being arranged in
series when viewed in the direction in which the member moves against said
adjustable force, said first switch element controlling the sequence of
the programmed gripper movement, and said second switch elements
consisting of a safety switch for disconnecting the handling device.
21. A handling device with a flexible gripper and having drive means for
moving said gripper, said drive means comprising a displaceable force
transmitting member, means for exerting an adjustable force on said member
for normally preventing movement thereof, said means permitting movement
of said member in response to stoppage of movement of said gripper when
the force thereon is greater than said adjustable force, switch means
responsive to movement of said member against said adjustable force for
controlling said drive means, and wherein said handling device is a fully
closed unit including a hydraulic and electric supply unit.
22. A handling device according to claim 21, wherein the hydraulic and
electric supply units are accommodated in a pillar and/or in an upper
frame connected with the pillar, thus enabling the height of the
underframe to be very small. |
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Claims |
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Description |
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The invention relates to a mechanical handling device with a flexible
gripper capable of carrying out certain activities. Handling devices of
this type have been used in connection with the most varied actions, for
example, when handling objects such as tools or components automatically
in order to reduce manual labour; or when handling radio-active objects,
that is to say when objects have to be dealt with which have to be kept
away from the human body and demand additional precaution in order to be
harmless to man. In order to be as versatile as possible, a handling
device should be capable of moving in all three spatial directions.
THE PRIOR ART
With known mechanical handling devices incorporating a gripper which can be
moved consecutively in various directions, the gripper movements are
controlled for example by means of trailing cams which move along with the
gripper, or by means of limit switches which actuate, on completion of a
pre-set gripper motion, a switch-element to initiate the next function.
Handling devices are also known which are used in conjunction with a
computer into which the gripper movements are fed. It is common to all
known handling devices that the distance covered by the gripper when
performing its movements is pre-determined, that is to say, the end
positions of the gripper are predetermined with each action. However, this
has certain severe drawbacks. It is, for example, impossible to stack up,
by the aid of one of the known handling devices, a number of objects,
because in such a case the gripper would have to execute a different
motion, covering a different distance, each time an additional object is
placed upon the last one on the stack. Similarly, the known devices are
not capable of placing a number of objects consecutively to form a
continuous row because, again, the distance covered by the gripper would
vary between one handled object and the next. If then, any of the known
devices were to be used for these purposes, the controlling switch-system
would have to be re-adjusted after each of the consecutive operations.
This, however, is too cumbersome and time-consuming to be practical. Apart
from these drawbacks, it is possible that the loading position which
corresponds to a given end position of the gripper is occupied for
whatever reason by another object. In such a case the gripper, advancing
towards its end position with its full energy, would damage or destroy at
least one of the two objects in question or even the handling device
itself. It is similarly necessary to ensure that the objects to be picked
up by the gripper during its consecutive reloading activity always occupy
exactly the same starting position, or the gripper might miss the objects.
Correspondingly, it is important that objects consecutively put down at a
given loading position should be removed without delay in order to avoid
their occupying the position too long. It is an additional drawback of the
known handling devices that they could cause damage to sensitive or
fragile goods, such as glassware, with slightly varying dimensions. This
is, however, inevitably the case with roughly finished objects. The
gripper, adjusted for a pre-determined distance to cover and not for the
dimensions of the articles handled, can easily cause damage when the goods
are put down in accordance with the pre-set length of the gripper
movement, missing the optimum position on, say, a base. These difficulties
restrict the range of application of the handling devices considerably:
The grippers can only perform certain movements as laid down by a given
repetitive program, which acts periodically in dependence on the completed
gripper movements. It is an additional drawback of handling devices
operated in conjunction with a computer or electronic calculator that
their manufacturing costs are very high. Finally, a grave danger is to be
taken into consideration: Any person standing in the vicinity of the
handling device in an unfavorable position could be pushed against a wall
or even pressed to death by a handling device whose grippers cannot stop
before reaching the end position. It is an aim of the present invention to
provide a handling device which is free from the drawbacks of the known
mechanical handling devices.
According to the invention, the problem has been solved by a drive system
associated with at least one of the gripper motions, the system comprising
a flexible member which can be displaced against the direction of an
adjustable force, so that it is moved against this force when an actuating
load, determined by the latter, acts on the gripper, said member also
operating a switch-element which serves for the control of at least one
movement of the device and/or the gripper. If the gripper touches a
mechanical resistance, for example, in collision with an object, the
displaceable member in the drive system is caused to move against the
adjustable force, actuating thereby the switch-element which releases,
say, the next gripper movement. In other words, the control of the gripper
motions is a function of force, and not a function of distance. The new
device is therefore capable, for example, of placing a number of objects
side by side, forming a row, because the gripper approaches the last of
the already positioned objects closely enough to be actuated by its
presence. The versatility of the new handling device, that is to say the
numerous actions it can carry out, becomes evident by the fact that the
handling device is capable of removing individual objects from a stack or
of adding further objects to an existing stack. In these cases the gripper
is actuated as soon as it is in contact with the stack, the latter
actuating a switch-element which orders the gripper, for example, to close
its jaws around a component. There is, moreover, no danger of persons
being injured by the mechanical handling device even in the event of a
gripper touching the person, because the order given by the actuating
force would become effective at the moment the impact occurs, and the
switch-element would react accordingly. It is an advantage to associate
individual movable members which are displaceable against an adjustable
force and capable of actuating a switching element, with a number of
gripper movements instead of providing only one of the gripper motions
with this facility; and it should be ensured that these switching elements
control the programmed movements of the gripper. A program of this kind
need not be periodical in relation to the distances covered by the
gripper, but it is periodical in relation to the forces which release the
gripper movements. In a way, the gripper itself acts as a feeler which
transmits the relevant information into the switch-element as soon as it
touches a resisting object. The actuating force directed against a first
gripper movement is thus transmitted by the gripper/feeler to the movable
member in the drive system which is associated with this first gripper
movement, and by its displacement the movable member operates the
switch-element which subsequently initiates a second gripper movement. The
mechanical handling device according to the invention can have a number of
efficient forms. For example, a gripper developed for swivelling motions
could advantageously be connected with, or rather rotatably fixed to, a
worm-wheel which engages with a motor-driven travelling worm, the latter
being axially displaceable, at least in one direction, against an
adjustable force so that the worm travels against this adjustable force
when the actuating load directed against the gripper is high enough, the
operating element which controls the switch being displaced at the same
time. The adjustable force can be produced, for example, by a spring
member in contact, at one side, with a fixed support and, on the other
side, with a working face which is movable together with the movements of
the worm. Or the adjustable force can be supplied by a piston through an
associated piston rod. The movements of the travelling spiral or worm are
preferably damped by means of a shock absorber.
According to an alternative arrangement, the swivelling motions of a
gripper could be effected by connecting the gripper -- again in a
rotatably fixed manner -- with a swivelling base to which a pivoted
bolster is fixed, the bolster swivelling together with the base around the
swival-axis of said base, and being rotatably fixed to a motor. Said
swivelling bolster can be displaced against an adjustable force by a
movement around its axis which extends parallel to the swivel-axis,
wherein the drive shaft of the motor, which is coaxial with the bolster
axis, is in frictional contact with a gear wheel which engages with a
fixed gear wheel having preferably an internal toothing and serving as a
bearing. When the actuating load is smaller than a given limiting value
determined by the adjustable force, the driving gear wheel is caused to
roll off on the fixed internal gear wheel, and this will cause both the
bolster and the base to which the gripper is connected, to swivel.
However, when the actuating load exceeds this limiting value, the driving
gear wheel and the drive shaft become stationary while the motor, together
with the bolster, revolve around the bolster axis, this rotational
movement operating a switch-element and acting against the direction of
the adjustable force. In other words, when a given actuating load acts on
the gripper, the drive shaft ceases to revolve around the swivel-axis
causing thereby the motor, and with this, the bolster to rotate in a
direction which is opposed to the direction of the adjustable force when
revolving around the drive axis. The adjustable force which acts on the
pivoted bolster can be produced in a number of ways, for example by a
suitable combination of piston and cylinder.
The linear gripper movements can be based on the gripper being connected
with a threaded nut, the tapped hole being parallel with the direction of
the linear movement, and the threaded portion of a spindle engaging with
the threaded nut, the spindle being axially displaceable against an
adjustable force, wherein a motor-driven gear wheel causes the spindle to
rotate. It therefore moves in the axial direction against the adjustable
force when the actuating load which affects the gripper is high enough,
the switch-element being moved at the same time by an operating member.
However, when the gripper collides with an object, the associated threaded
nut ceases to travel along the spindle, and the latter moves through the
threaded nut in a direction against an adjustable force. With vertical
spindles, which correspond to linear gripper movements in the vertical
direction, a loading member, say a spring, is advantageously used in an
upward direction, to counteract the gravitational force. By this
precaution the spindle can be protected against excessive gripper loads
when the latter, together with the parts moving with it, travels downward
at a speed where the force of inertia becomes immaterial. The loading
member which acts on the spindle in an upward direction thus balances in a
way the weight of the gripper including the parts which are loading the
spindle together with the gripper. It follows that the spindle is affected
by the resultant difference of forces, i.e. between the downward force due
to the weight of the gripper including the parts which move with it, and
the upward force exerted by the loading member. Since the loading member
is adjustable, this force-difference is variable and corresponds to the
adjustable force against which the spindle moves upwards as soon as the
gripper rests on an object.
Alternatively, the linear gripper movements can be based on the gripper
being connected with a motor-driven gear wheel whose drive axis extends at
right angles to the gripper motion, the gear wheel engaging with a toothed
rack which is adjustable in relation to an adjustable force, in its
longitudinal direction. The rack will therefore move against the
adjustable force when the actuating load directed against the gripper is
sufficiently high, the operating member controlling the switch-element
being moved at the same time. This arrangement is particularly effective
when grippers have to perform vertical movements at great speed. With
these vertical movements the forces of inertia play a considerable part,
the gripper moving downwards, together with the parts which are connected
with it, at a speed which is so great that the weight of these parts is
almost compensated by the forces of inertia. In these circumstances the
piston rod of a piston in a stationary cylinder can efficiently control
the upper portion of the toothed rack: The piston rod forces the toothed
rack downwards during the rapid downward movement of the gripper, whereby
the total load resulting during this process, an adjustable force, which
maintains the toothed rack in its correct position, is composed of the
downward directed force-difference between the load exerted by the piston
rod and the weight of the gripper including the parts moving with it,
which is reduced by the effect of the forces of inertia. As pointed out
above, this embodiment is favourable for rapid gripper motions. In
practice, the gripper will be allowed to move towards the object it has to
handle at a high speed until it approaches it rather closely, when the
gripper movements will be slowed down in order to avoid the danger of
destruction. The piston which forces the toothed rack downwards will
therefore be under pressure during the first phase only, i.e. during the
rapid downward movement of the gripper, while the pressure will be removed
during the second phase when the gripper movement is delayed. The
advantage of this arrangement is that sensitive objects are protected
against damage which, in a system where pressure is applied to the piston
during both the rapid and the delayed phases, would be inevitable, the
downward load, composed of the gripper weight, the weight of the parts
which move with the gripper, and the piston load, being so great that the
toothed rack cannot move upwards before the actuating load directed
against the gripper reaches a very high value. When using the arrangement
according to the present embodiment of the invention, however, the gripper
moves initially at a high speed, this being the phase while the piston is
loaded; when the gripper approaches a certain point in the vicinity of the
loaded object, its movements are delayed by removing the pressure from the
piston. movements cross-head. In systems where the gripper is supported by
an arm which is linearly and horizontally displaceable in a compound head,
(the latter being flexibly supported by a pillar which is pivoted at an
underframe, said compound head being capable of moving linearly in the
vertical direction) it is advisable for at least the drive correlated with
these vertical movements of the cross-head and the drive which is
correlated with the rotational movements of the pillar, to comprise a
moveable member which can be displaced against an adjustable force.
Similarly, a drive comprising such a moveable member could advantageously
be associated with the horizontal, linear, movement of the arm in the
cross-head. When a handling device is equipped with these facilities, the
gripper can be made to move in any of the spatial directions, wherein the
distance covered in any particular direction depends solely on the
activating load which is applied to the gripper. The arm holding the
gripper could advantageously be telescopic in such a manner that the end
of the arm which lies away from the gripper is stationary when the gripper
moves towards the compound head. The space occupied by the mechanical
handling device is thereby considerably reduced because there is no need
for a swivelling-space to be kept free at this end of the arm. An
additional advantage is gained with a system where a drive for one gripper
movement contains a flexible member that is displaceable against an
adjustable force, when this contains two individual switch-elements which,
seen in the direction in which the movable member is displaced, are
arranged in series, the first switch-element controlling the program for
the gripper movements, and the second acting as a safety switch capable of
disconnecting the handling device. The second switch-element will switch
off automatically the mechanical handling device when the first
switch-element which controls the gripper movements breaks down for
whatever reason. This mechanical handling device is in fact completely
self-contained, incorporating hydraulic and electric power systems; the
only external source is a power line which leads into the handling device.
In order to maintain the height of the underframe as small as possible,
the hydraulic and electric supply units are conveniently accommodated
inside the pillar or in a upper frame section connected with the pillar.
The underframe merely houses the hydraulic and electrical connections to
the drives contained in the underframe. The small height of the underframe
enables the gripper to pick up objects from floor level of another very
low position. The mechanical handling device discussed above ranges among
the stationary devices. Its location is fixed. However, the layout is such
that the handling device can be used as a mobile unit, since a special
base, for example rails, can be incorporated into the system, which enable
the entire mechanical handling device, i.e. the underframe and all other
parts of the handling device, to be moved about, a drive incorporating a
flexible member which can be displaced against an adjustable force and a
switch-element being associated with the displacement of the handling
device. A handling device having these characteristics is therefore
capable of taking, for example, components which are rough machined in a
first machine-tool to a second machine tool located at some distance, to
be finished there.
The description of the gripper itself is contained in the discussion of the
accompanying drawings which follows below, to describe the invention in
greater detail.
FIG. 1 shows a handling device in elevation, with one half of the pillar
removed;
FIG. 2 is a front view of the handling device according to FIG. 1;
FIG. 3 is a section along line III--III in FIG. 1, of a first embodiment of
a drive for swivelling motion;
FIG. 4 is a section along line IV--IV in FIG. 3;
FIG. 5 is a section along line V -- V in FIG. 3;
FIG. 6 is a section along line VI--VI in FIG. 7, which is a second
embodiment of a drive for swivelling motions;
FIG. 7 is a plan showing the second embodiment according to FIG. 6;
FIG. 8 is a section illustrating a first embodiment of a drive for linear
movement;
FIG. 9 is a section along line IX--IX in FIG. 10, which is a second
embodiment of a drive for linear movement;
FIG. 10 is a section along line X--X in FIG. 9;
FIG. 11 shows the gripper from above in a plan;
FIG. 12 is a section along line XII--XII in FIG. 11; and
FIG. 13 is a section along line XIII--XIII in FIG. 12.
FIGS. 1 and 2 show the handling device in a front- and side elevation
respectively. As underframe 1 supports a pivoted pillar 2 which may
consist of two sections 2a, and 2b, a first motor 9 driving the pillar in
rotational movement. The pillar 2 supports a compound head 4, which is
vertically adjustable, parallel with the longitudinal axis 3 of the
pillar. These adjustments are made by the aid of a guide-way 5, such a
guide-way being associated with each of the two sections 2a, 2b of the
pillar, and by the aid of a cross-head spindle 6 which extends through a
threaded nut (not shown in the drawings) which is connected with the cross
head 4, the spindle being driven by a second motor 7 which is located at
the upper frame member 8. The cross-head 4 carries an arm 10 which extends
at right angles to the longitudinal axis 3 of the pillar 2, a spindle
bearing 11 being fixed to the arm and supporting, rotatably, a spindle 12
which extends through a threaded bore in the cross-head 4, a third motor
13 causing it to revolve, whereby a rotational movement of the its 12
displaces the arm 10 in the direction of is axis. A gripper tube 14,
accommodated in a longitudinal bore through the arm 10, is connected, at
one end, with a fourth motor 16 through a coupling (clutch) 15 and, on the
other side, with a gripper 17. With the clutch 15 thrown into gear, the
gripper tube 14, and with it the gripper 17, can be caused to rotate
whereas with the clutch 15 disengaged a torsional moment exerted on the
gripper 17 makes the latter freely rotatable around its longitudinal axis.
The gripper 17 is connected with the gripper tube 14 by a rotational shaft
18 which extends at right angles to the gripper tube axis. Thus the
gripper 17 is able to perform a rotational movement around the
longitudinal axis 3 of the pillar 2, and it can be vertically displaced
along the pillar 2. In addition to this, the length of the pivoted arm can
be varied, and the gripper can revolve around two of its axes. It is due
to this great freedom of movement that the gripper can perform the most
varied actions, the sequence of programmed operations being automatically
controlled. The gripper itself acts as a transducer, and all information
related to switching is transmitted by the gripper itself. Thus each time
a resisting object induces into the gripper a given actuating load, the
corresponding information is transmitted into a switch-element which
initiates the next gripper movement. The information which announces that
a given actuating force is directed against the gripper can be transmitted
into the switch-element by a number of methods, as explained below. Since
it is the gripper itself which picks up the information, the gripper can
perform, not only a sequence of movements covering the same distance, but
it can also move, without any external control, over paths whose lengths
vary between very wide margins. The relevant factor for the distance which
can be covered by the gripper is the fact that the gripper collides with a
resisting object.
FIGS. 3 to 5 deal with the information concerning a gripper which collides
with an object while swivelling around the longitudinal axis 3 of a pillar
3, describing the manner in which the information is processed in order to
be transmitted to a switch-element 30 or 30a.
FIG. 3 shows an underframe 1 in section along line III--III in FIG. 1. A
wormgear 19 pivoted in the underframe 1 is connected in a rotatably fixed
manner with the pillar. As shown in FIG. 5, the worm-gear 19 is keyed on
to a rotary table 90 which is pivoted in the underframe 1 and supports the
pillar, which is not shown in the drawing. Together with the pillar it
carries, the rotary table 90 revolves around a fixed shaft 91. The worm
gear 19 may be driven through a travelling worm 20 which in turn is driven
by the first motor 9. On one side the travelling spiral 20 is keyed on to
the drive shaft 21 of the motor 9 through a cotter 22 and on its other
side it is keyed on a fulcrum pin 28 which is pivoted on, and axially
fixed to, the underframe 1. The travelling worm 20 is thus supported in an
axially flexible manner, its instantaneous positions being fixed by coil
springs 23. The adjustable force through which the travelling worm is
retained in its correct position can alternatively be produced in a
different manner using, for example, a suitable combination of piston and
cylinder. The coil springs 23 are supported, on one side, against a
stationary stopping surface 24 and, on the other side, against an
adjustable working face 25 which can move along together with the
travelling worm 20. The working face 25, in the embodiment shown as an
example, is located on a sleeve 26, which is rotatable around a travelling
helix, the sleeve end lying away from the coil spring 23 being rotatable
in relation to a step in the worm, a ball bearing 27 being used as an
intermediate member.
The travelling spiral 20 thus is maintained in its central position by
adjustable forces acting at either end. In this position, the worm 20
causes the worm wheel 19 and consequently also the pillar, to rotate as
soon as the motor 9 is switched on. When the gripper, which revolves
together with the pillar, collides with a resistance, the travelling worm
20, reacting to an actuating load which is induced into the gripper
through the spring load of the coil spring 23, ceases to drive the
worm-wheel 19; instead, the travelling worm 20 moves in an axial direction
against the adjustable spring load. When the worm-wheel revolves in
accordance with arrow 28 for example, the worm 20, reacting to a given
actuating load exerted and affecting the gripper, will move towards the
right hand side as indicated by arrow 29. When the worm-wheel 19 revolves
in the opposite sense, the worm 20 is caused to move in the opposite
direction. The movements of the worm cause a switch-element, 30 or 30a, to
react and control the programmed sequence of operations. There are, in
fact, two parts which move in relation to one another, namely the
worm-wheel 19, and the worm 20. The worm or travelling spiral will perform
its axial movements, and the worm-wheel will be stationary, when the
torsional moment produced by the travelling worm, in order to make the
worm-wheel revolve, is so great that the spring load in the springs 30
cannot maintain the worm in its central position; the travelling worm
travels in this case past the worm-wheel, the two threads being engaged.
FIG. 4, which is a section along line IV--IV in FIG. 3, shows how the axial
movements of the travelling worm can be damped by means of a shock
absorber. This shock absorber incorporates a piston 31 to which power can
be admitted from either end; this corresponds to the two opposed
directions in which the travelling worm moves. The piston is rigidly
supported, the two piston rods 32, 33 being fixed to the underframe 1. In
addition, the shock absorber comprises a damping cylinder 34 which extends
parallel to the travelling spiral 20, the two cylinder covers 35, 36,
being in frictional contact with the travelling worm, in the axial
direction; this contact is made through an annular part 92 at either end,
which ensures that the rotational freedom is available. Each of the two
annular members 92 surrounds the travelling worm and rests at the same
time, at one of the axial ends, against the bottom of a sleeve 26. The two
pressure chambers located between the two covers and the piston ends
receive the two pressure lines, one of them opening into one of the
pressure chambers, and the second into the other pressure chamber and both
comprising a restricting zone 37, 38 respectively. When the travelling
worm and consequently the damping cylinder 34 move, say, towards the right
hand side, the pressure medium in the right hand side pressure chamber is
displaced and the movement of the travelling worm is correspondingly
damped.
Another way by which to transmit the information that the gripper,
swivelling around the longitudinal axis 3 of the pillar 2 has met with
resistance, is shown in FIGS. 6 and 7 at an apex-element. FIG. 6 shows, in
cross-section, a swivel-base 93 with a swivelling shaft 39. The pillar,
which is not shown in this illustration, is rigidly fixed to the
swivel-base 93, and any rotational movements of the base 93 consequently
entail a rotation of the pillar. The swivel-base 93 is furthermore
coaxially rotatable in relation to a fixed bearing 44. The fixed bearing
shown in FIG. 6 is an internal gear wheel. However, an external gear wheel
would be equally suitable for this purpose. The fixed bearing 44 is
rigidly mounted on the underframe 1a. A pivoted bolster 45, fixed to the
swivel-base 93, is rotationally fixed to a motor 9a. The drive-shaft 43 of
this motor extends through an opening in the swivel-base 93, and supports
a gear wheel which engages with the internal gear bearing 44. The
drive-shaft 43 is supported on the swivel-base 93 -- through a ball
bearing 48 and a special insert 42 -- in such a manner that it c | | |
