Note: Descriptions are shown in the official language in which they were submitted.
11~12~Z
ER ~EED ROTARY ~`OOL"
~his invention relates to a power feed rotary
tool, where the wor~ing head of the tool is rotated
by an electric ~no1;or, and is fed towards the work-
piece pnewnatically. ~he tool will noLmally be a
drill or a tapper, but the invention could also
be applied to a screw-driveI or a nut-runner, with
or without torque control.
~he i~lvention is a deve~opment of a power-feed
drill described in our earlier British Patent 956 081.
~his patent describes a drill where both drill
rotation and feed are pneumatically operated. In
many instances where a number of such tools are
used, the volume of compressed air which is available
prevents the use of additional, completely pneumatically
operated tools. ~he use of an electric motor to
replace the high air consumption rotary pneumatic
drive can avoid this problem.
Rotary tools of this type are fre~uently combined
in a jib to form a unit capable of drilling a number
of adjacent holes simultaneously in a workpiece. In
such applications, it is important that the individual
tools can be closely spaced, and that the controls for
adjusting the depth of feed of each tool be still
accessible.
According to the invention, there is provided a
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po-vJer feed rotary tool having an electric motor
for rotating a working head of the tool, and a pneumatic
system for feeding the working head -towards a workp;ece,
the tool having an elongate housing w;th the working
head at one end of the housing, a drive tra;n wilh;n
the housing for rotating the working head, a p;ston
within the housing for displacing the working head,
as it rotates, towards the workpiece, a control rod
at the other end of the housing which is restrained
from rotating, but is cor~ected to the drive train so
as to be displaced together with the working head,
the control rod including an abutment for limiting
the displacement of the working head, the electric
motor being drivingly connected to the drive train
between said ends of the housing.
~ his arrangement, with the control rod extending
from the top of the housing 7 makes adjustment of the
feed of the working head very easy because no matter
how many other tools are surrounding a particular
tool, the control abutment is always accessible for
adjustment. ~his has always been the case in comple- j
tely pneumatically operated tools. In the case of
pneumatic tools~ the rotary air motor which rotates
the working head can be accommodated completely
within the elongate housing and spaced from the
working head just sufficiently to leave enough space
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for the necessary gears. There is therefore no problem
in providing a non-rotating control rod which is
displaced with the wor~ing head and which can be
connected to the stator of the motor. ~owever, an
electric motor with the necessaLy power OUtpllt is of
a si~e which must be ~ounted externa]ly of the elonga~te
housing. An externally mounted motor is asy~netrica]
re]ative to the axis of the tool and it is not
practical to move the motor rogether with the dis-
placement l~ovement of the working head.
In a preferred embodiment, the control rod is
connected to the drive train via a thrust bearing
on the side of the motor driving connection nearest
to said other end of the housing. ~he control rod
itself can be restrained outside the housing against
rotation, and the bearing enables the drive train to
continue rotating while the control rod is held stationary.
In an alternative form of embodiment, which may
be used with the previously described thrust bearing
or on its own, a tie rod extends parallel to the
displacement axis of the tool between a part fixed
to the control rod and a part on the opposite side
of the motor drive connection which does not rotate
but is-displaced together with the working head.
~he driving connection between the motor and
the drive train is preferably by means of a toothed
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belt run~ing around appropriately toothed pulleys
on the motor output shaft and part of the drive
train. A specia]ly adapted device ~ay be provided
to tension the drive belt. This dev;ce can be
p1ugged ;nto a dr;ve belt housing, and can be opera-
ted to pull the motor plate in the direction of
tensioning the belt lmtil the spring force of a
spring contained in the device is overcome to
indicate that the correct tension has been reached
in the belt.
It is very advantageous if the control top of
the tool can be rotated relative to the rest of the
tool. The control top includes the control rod and
operating controls and connections to external
services. In one preferred form of the invention,
the control top is attached to the elongate housing
by means of a sleeve having threads of opposite
hands at its two ends. At one end, this sleeve
screws onto a corresponding -thread on the end of
the elongate housing, and at the other end the
sleeve screws onto a corresponding thread on the `
control top. A spacer is positioned between the
housing and the control top. To alter the position
of the control top, the sleeve is slackened suffi-
2~ ciently for the control top -to be manually turned
through the desired angle. Once the control top
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is in the correct position, the sleeve can be ti~htened up
against the spacer to hold the top in the correct angular
position. Although threads of opposite hand are preferred,
the threads could be of the same hand with little differ-
ence in -the ~ay that this rotation is carIied out.
The invention wi]l now be further ~cscribed, by
way of exarnp1e w;th refelence to the accompany;ng
drawings, in which:
~ igure 1 is a cross--section through part of a first
embodiment of rotary tool according to the inventionj
~ igure 2 is a cross-section through part of a second
embodiment of a rotary tool according to the invention;
and
~ igure 3 is a schematic illustration of a belt
tensioning device according to the invention.
In ~igures 1 and 2, the tool has been foreshortened
for ease of illustration. ~he lower end of the tool
is not shown, but this will be conventional, and will
carry a working head at its lower end. Reference may
be made to our British Patent 956,081.
~he tool is driven by an electric motor 1. ~his
motor is mounted on a casing 2 which is rigidl~
attached to the elongate tool housing 3. The motor 1
drives a toothed pulley wheel 4, and a toothed belt
5 runs around the pulley wheel 4 and around another
pulle~ wheel 6 on the axis of the tool. ~he motor 1
is supported on the casing 2 on a motor plate 7. ~he
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plate 7 is secured by a number of bolts 8 with mlts
9 which pass through elongate holes in the plate 7.
When the nl~ts 9 are slackened, the plate 7 can be
moved in the direct-;on of -tensioning or slackening
the belt ~. For corre~t operat;on of the d-rive, it
is ;mportant t}lat the belt should be at the correct
tension. ~igure 3 shows a device wh;ch can be fitted
to the casing 2 to produce the correct tension. ~he
device shown in Figure 3 has a base 10 with retaining
studs 11. ~he studs 11 fit into correspondingly
shaped recesses 12 in the underside of the casing 2.
~he device in ~igure 3 also has abut~ents 13 which
contact the side wall of the casing 2, and a threaded
adjusting screw 14 which engages in a threaded bore
15 in the motor plate 7. The adjusting screw 14 has
a knob 16, and a compression spring 17 is arranged
in the device as shown. ~o tension the belt, the
nuts 9 are slackened so that the motor plate 7 is free
to slide. ~he device is then attached to the casing
2 with the lugs 11 in the recesses 12 and the abutments
13 against the casing side. As the screw 14 is screwed
into the threaded bore 15, the plate 7 is moved towards
it. As the tension in the belt 5 increases, it becomes
progressively more difficult to pull the plate 7 against
the tension of the belt, and the spring 17 will compress
as the knob 16 and screw 14 continue to be turned. ~he
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knob 16 has a projection 18. When the desired
tension in the belt 5 has been reached, this projec-
l;ion 18 engages between flanges on -the face 19 of
the device and prevents fur-ther rotat;on. ~hen
this condition has bcen reached, the nuts 9 can be
tightened, and once they have been tightened t,he
dev;ce of Figure 3 can be ren~oved from the tool.
~he device thus provides a si~ple and accurate way
of achieving -the correct tension in the belt 5. ~he
spring 17 can be choosen so that its cha~acteristics
produce the desired tension in the belt. For
different sizes of tools, different belt tensions
may be necessary, and therefore devices with springs
17 of different characteristics can be employed.
The pulley wheel 6 has flanges 20 for locating
the belt correctly on the pulley. ~he pulley wheel
itself is carried in bearings 21 in a fixed housing
part 22 which is in fact integral with the mo-tor
pulley casing 2. ~he pulley wheel 6 has an internal
bore with splines 2~ which engage with a splined
spindle 24. ~he spindle 24 can move longitudinally
through the pulley 6 while the splines maintain a
driving connection. ~he spindle 24 is connected to
the working head (not shown) of the tool, and transmits
the necessary rotation from the motor 1.
To provide the feed motion, compressed air is
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;ntroduced into the tool via an inlet 25 in the
control top 26. ~he compressed air is fed through
passages (not shown) to a chamber 27, and from
cha~ber 27 ia a passage 28 to another chamber 29.
Within the chamber 29, there is a piston 30 with
a piston seal 31, and when pressure builds up in
chamber 29 the piston 30 is displaced downwards
together with the spind]e 24, which thereby slides
through the splines 23.
~ A control rod 32 extends from the top of the
tool above the control top 26. A cross head 33 is
clamped to the control rod 32, but can be unclamped
and slid along the length of the control rod to
provide a coarse stroke adjustment. A guide pin
34 is fixed in the control top 26 and slides through
a bore 35 in the cross head 33, to restrain the
control rod 32 from rotating, but to permit the
control rod to be displaced along the axis of the
tool.
~he control rod 32 iS connected to the upper
end of the spindle 24 by a thrust bearing 36. ~ooking
at the assembly around the thrust bearing 36 in more
detail, it will be seen that the central bore of the
control rod 32 is enlarged, and has a plug 37 at its
bottom end which forms an abutment for one side of
the bearing 36. As the spindle 24 is moved downwards
through the pulley wheel 6, it will therefore pull
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the control rod 32 wi-th it. Since the control rod
32 iS prevented from rotating by the guide pin 3L~,
there will be relative rotation between the spindle
24 and the control rod ~2 at the thrust bearing 36.
With the de-vice s]-~own, it is possible to lotate
the control top relative to the rest of the tool.
It will be appreciated that the tool is as~metric
because of the presence of the electric motor 1 on
one side. When a number of tools are mounted close
together to form a unit, they may have to be mounted
with the electric motor on each tool facing away
from the area of the workpiece. In order to enable
the adjust~ents, which are available at the control
top, to be set for all the tools simultaneously, it is
convenient if the control top of each tool can be rota-
ted so that the control tops on all tools are in the
same relative orientation to an operator at one side
of the unit. To this end, a sleeve 38 is used to
connect the control top 26 and the housing part 22. ~he
sleeve 38 has threads of opposite hand at each end which
mate with corresponding threads on the control top
and the housing part 22, respectively. A spacer 39
is provided between the housing part 22 and the
control top. In order to alter the orientation of
the control top relative to the tool, the sleeve 38
is unscrewed, and an aperture 40 is provided in the
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circumference of the sleeve for engagement by a
suitable tool. Once the sleeve 38 has been slackened,
the control top can be rotated by hand -to the correct
orientat;on, and the sleeve 38 can tnen be tightened
up aga;nst the spacer ~9 to lock the control top
in its new orientation~
The tool shown in ~igure 2 is of a larger rating
than that shown in ~igure 1, and it will be im~nediately
apparent that the electric motor 1a is of a larger
size relative to the tool housing.
In ~igure 2, many parts are the same as in ~igure
1, and so they will be designated by the same reference
numerals.
With the tool shown in ~igure 2, the thrust
bearing 36 may not be man enough for the job. ~o
explain why this is so, it is first necessary to be
aware that hydraulic check units may be fitted to
these tools in the region of the control top. ~he
hyraulic check unit is normally set to come into
operation just before the drill tip breaks through
the workpiece, to check the speed of advance of
the drill at the moment of breakthrough. When
drilling with the check unit in operation, a
considerable load will fall on the thrust bearing
36 because pneumatic pressure is operating to push
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the spindle 24 downwards, whereas the resilience of
the hydraulic check unit is operating to prevent the
control rod 32 from being Inoved downwards.
Because of this problem, the tool shown in
~igure 2 is provided with a t;e rod 4-1 extending
between the cross head 33 and a part 42 which MOveS
with the piston 30. Neither the part 42 nor the
piston 30 rotate during operation of the tool. ~he
tie rod 41 passes through a sleeved bore 43 in -the
~otor drive pu]ley housing 2. ~his tie rod prevents
excessive strain being put on the thrust bearing 36,
and may make it possible to dispense with the thrust
bearing 36 altogether. When the tie rod 41 is in
position, the cross head 33 and piston 30 both
advance together at the same speed. ~he use of tie
rod 41 can make it possible to dispense with the
guide pin 34 shown in ~igure 1.
~he electric motor 1 or 1a is of a standard type
which is readily available commercially. It is
possible to exchange the drive pulley 4 for another
pulley of a different diameter in order to alter the
transmission ratio.
Because the control top and control rod in the
tools described can be constructed identically with
pneumatically driven tools, it is possible to arrange
both pneumatically and electrically driven tools
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12
together in the same unit, and to carry out identical
adjustments for both types of tool. This can be a
very sign;ficant advantage when electrically driven
tools are used in places whe:re pneu~atically driven
tools are already in use, and where no more pneumatic
tools can be used because of a shortage of comp-essed
air.
