Apparatus, especially portable apparatus, for handling tubular- and/or rod-shaped workpieces or the like

An apparatus is provided for machining tubular and/or rod-shaped workpieces. The apparatus has a rotational drive or motor for the workpieces to be machined. A switching device, which is accommodated in, and actuated by, a foot pedal, is connected to the rotational drive. The foot pedal is provided with a restart arrestor, and/or an emergency shutoff device to provide protection against unintended restarting of the apparatus after a power failure, or to instantaneously disconnect the apparatus from the electric circuit in case of danger.

The present invention relates to an apparatus, especially a portable 
apparatus, such as a thread-cutting machine, for handling or machining 
tubular- and/or rod-shaped workpieces or the like. The apparatus has a 
rotational drive and a switching device for the rotational drive; the 
switching device is accommodated in a foot pedal which is provided with a 
foot lever for actuating the switching device. 
This known apparatus is a portable thread-cutting machine, the rotational 
drive of which is turned on, by actuating the foot lever, to rotate the 
workpieces to be machined about their axes. When, for example after a 
power failure, the electric circuit is connected again, the rotational 
drive of this apparatus can unintentionally start again. 
It is known with machines having protective control to install for example 
switch protection with self-holding means which drop out during power 
failure, so that after switching on the electric circuit, the machine does 
not start again. Such switch protection means however have relatively 
large dimensions, and are therefore especially unsuitable for portable 
devices which have no space available for such large additional parts. The 
installation of such switch protection would also require considerable 
modification of the apparatus. 
It is an object of the present invention to embody an apparatus of the 
aforementioned type in such a way that in the event of a problem or 
danger, the apparatus itself does not become a source of danger to the 
operator, and to do so without requiring extensive modification of the 
apparatus.

The apparatus of the present invention is characterized primarily by either 
providing the foot pedal with an emergency shutoff device which has an 
operating element, or with a restart arrestor against unintentional 
restarting following correction of a power failure. 
When the rotational drive is turned on and the power fails, the rotational 
drive is also shut off. With the second alternative mentioned above, the 
restart arrestor prevents the apparatus from being turned on after 
elimination of the operating problem and connection of the electric 
circuit. The operator of the apparatus must first actuate the restart 
arrestor, so that the circuit of the switching device is closed. Since the 
restart arrestor is provided at the foot switch, the apparatus itself need 
not be modified. Consequently, apparatus already being used can also be 
subsequently equipped with such a restart arrestor in accordance with the 
present invention. 
By providing the foot pedal with an emergency shutoff device according to 
the first mentioned alternative of the present invention, the emergency 
shutoff device can be actuated in an emergency situation by the operating 
element, so that the apparatus is disconnected from the power supply, and 
the rotational drive is instantaneously turned off. Even if the switching 
device of the apparatus is actuated by the foot pedal, the rotational 
drive cannot be turned on. In order to restart the apparatus, the 
emergency shutoff device must again be switched on. The emergency shutoff 
device is provided at the foot pedal, so that a modification of that part 
of the apparatus provided with the rotational drive is not necessary. 
Consequently, apparatus already being used but not equipped with an 
emergency shutoff device can very easily be subsequently provided with 
such an emergency shutoff device. It is merely necessary to disconnect the 
connecting cable provided with the foot pedal, and to connect the 
connecting cable of the foot pedal of the present invention. 
According to further features of the present invention, the restart 
arrestor may be accommodated in the foot pedal. More specifically, the 
restart arrestor and the switching device may be accommodated in a common 
housing, with the restart arrestor preferably being arranged above the 
switching device. The restart arrestor and the switching device may be 
accommodated in separate receiving chambers which preferably merge with 
one another; preferably, the lower receiving chamber, viewed in the 
longitudinal direction of the foot pedal, extends beyond the upper 
receiving chamber. 
The restart arrestor may be separated from the foot lever by an end wall of 
the housing; this wall preferably separates the upper receiving chamber 
from the foot lever, and is provided at approximately half the length of 
the lower receiving chamber; this end wall extends from an upper wall of 
the housing and terminates at a distance from a bottom part of the foot 
pedal. 
The restart arrestor may have a release button which is shiftable against 
spring force for switching-on the restart arrestor; the release button may 
project outwardly through the housing. 
An upper wall may be connected to the end wall and may extend in the 
longitudinal direction of the foot pedal and partially close off the top 
of the lower receiving chamber; this upper wall preferably lies externally 
of the upper receiving chamber, and may be connected with the bottom part 
by another end wall. 
The restart arrestor may have a relay with a self-holding circuit which 
lies in the circuit of the switching device. 
With the embodiment in which the foot pedal is provided with an emergency 
shutoff device having an operating element, the emergency shutoff device 
may be accommodated in the foot pedal, and the operating element may be 
actuated from the outside. The emergency shutoff device and the switching 
device may be accommodated in a common housing, with the emergency shutoff 
device being arranged above the switching device. The emergency shutoff 
device may be separated from the foot lever by a wall of the housing. The 
emergency shutoff device and the switching device may be accommodated in 
separate receiving chambers of the housing. The emergency shutoff device 
and the restart arrestor may be accommmodated in a common receiving 
chamber of the housing. 
Referring now to the drawings in detail, the apparatus shown is a portable 
external-thread-cutting machine for tubular and/or rod-shaped workpieces 
or the like. The apparatus has a base 101 upon which is arranged a chuck 
102, the clamping jaws 103 of which securely grip the workpiece to be 
machined. The chuck 102 is provided with a rotatable clamping lever 104 to 
effect clamping. A cutting head 105 is mounted axially shiftable on the 
base 101; this cutting head 105 is rotatably driven by a motor 106. A 
rotatable feed lever 107 is provided to axially shift the cutting head 105 
on two guides 108, 109 on the base 101. The cutting head 105 is provided 
with radially displaceable cutting jaws 110 with which a thread can be cut 
on the workpiece. 
The thread-cutting machine is electrically connected to a foot switch or 
pedal 2 by a connecting cable 1, as shown in FIG. 1. The foot pedal 2 has 
a housing 3 which extends over the entire height of the foot pedal 2 and 
is preferably made of synthetic plastic material. As shown in FIG. 3, the 
housing 3 has an end wall or front plate 4 which extends over the entire 
height of the foot pedal and is disposed transverse to the longitudinal 
median plane of the foot pedal. The upper end of the end or front wall 4 
merges approximately at right angles with an upper wall 5 of the housing; 
this wall 5 continues into an upper wall 6 of a hood 7. The upper wall 5 
has a rectangular outline or contour, with the longer sides extending 
transverse to the longitudinal median plane of the foot pedal 2. The upper 
wall 6 of the hood 7 extends from the housing 3 towards its free end with 
a slight rise, so that the upper wall 6, as viewed in the direction 
towards its free end, has an increasing spacing from the bottom part 8 of 
the foot pedal 2. As shown in FIG. 2, the hood 7 has a U-shaped cross 
section, and has sides 9, 10 which diverge from the upper wall 6 and 
terminate at a distance above the bottom part 8. The height of the sides 
9, 10 is slightly greater than the greatest half-height of the foot pedal 
2. The sides 9,10 have a curved transition into the upper wall 6 of the 
hood 7. Additionally, the sides 9,10 converge from their free ends toward 
the housing 3, and have a curved transition into the sidewalls 11, 12 of 
the housing 3, which sidewalls 11, 12 are parallel to each other and 
approximately at right angles to the end wall 4. The side walls 11, 12 are 
additionally connected approximately at right angles with the bottom part 
8, which has a rectangular outline or contour, and the underside of which 
is provided with feet 13 in the vicinity of the corners thereof. The 
bottom part 8 terminates with the end wall 4 and the sidewalls 11, 12, and 
extends approximately as far as does the free end of the hood 7. A further 
end wall 14 is located across from the end wall 4, as can be seen in FIG. 
3. This end wall 14 is parallel to the end wall 4 as well as at right 
angles to the upper wall 5 of the housing 3, and extends over a little 
more than half the height of the foot pedal 2. An upper wall 15 is 
connected at right angles to that end of the end wall 14 remote from the 
upper wall 5. This wall 15 extends from the end wall 14 toward the free 
end of the hood 7, and is nearly parallel to the bottom part 8. The upper 
wall 15 is connected with the bottom part 8 by an end wall 16 which is 
connected with the wall 15 at right angles. The distance between the two 
end walls 4 and 14 corresponds to approximately 1/3 to 1/4 of the length 
of the foot pedal 2. The length of the upper wall 15, measured in the 
longitudinal direction of the foot pedal 2, likewise corresponds to 
approximately 1/3 to 1/4 of the overall length of the foot pedal 2. The 
height of the end wall 16 is slightly less than the length of the foot 
pedal 2 measured at this location. The end wall 14, the upper wall 15, and 
the end wall 16 connect the sidewalls 11, 12, which are located across 
from each other, so that a high rigidity of shape is attained. 
The housing 3 is delimited by the end walls 4 and 14, the upper walls 5 and 
15, the sidewalls 11, 12, a portion of the bottom part 8, and the end wall 
16. The end wall 14 additionally forms an end wall of the hood 7. As a 
result of the described configuration of the housing 3, two oppositely 
located receiving chambers 17, 18 are formed which respectively extend 
over the entire width of the foot pedal 2. The upper receiving chamber 17 
is only approximately half as long as the lower receiving chamber 18 when 
viewed in the longitudinal direction of the foot pedal 2, and the height 
of the receiving chamber 18 is slightly less than the height of the upper 
receiving chamber 17; the chamber 18 extends into the region of the hood 
7. A very compact construction of the foot pedal 2 is attained as a result 
of this divided housing. 
A switching device 19 is installed in the lower receiving chamber 18, and 
is connected with the connecting cable 1. A restart arrestor or blocking 
means 20 is arranged in the upper receiving chamber 17, and is provided 
with a release button 21 which projects outwardly through an opening 22 in 
the upper wall 5 of the housing 3. The release button 21 can be pressed 
against spring force. The end wall 4 has an opening for the connecting 
cable 1 in the region of the lower receiving chamber 18. 
A foot lever 23 for actuating the switching device 19 is pivotally mounted 
on a bearing bolt 24 against spring force in the region below the hood 7. 
The foot lever 23 is plate-shaped and has on its underside a projection 25 
which actuates a switch 26 of the switching device 19 when the foot lever 
23 is pressed down against spring force. The U-shaped configuration of the 
hood 7, and the converging sides 9, 10 of the hood, assure that the 
operator can comfortably place a foot on the foot lever 23 below the hood 
7 and can actuate the foot lever 23. 
The hood 7, the end wall 14, the upper walls 5 and 15, as well as the upper 
portions of the end wall 4 and the side-walls 11, 12 are made in one piece 
and are detachably connected with the lower part of the foot pedal 2. The 
upper portions of the end wall 4 and the sidewalls 11, 12 have the same 
height as the end wall 14. The lower part of the foot pedal 2 is formed by 
the bottom part 8, the end wall 16, and the lower portions of the end wall 
4 and the sidewalls 11, 12. In the assembled state, the end faces of the 
lower portions of the end wall 4 and of the sidewalls 11, 12 adjoin the 
end faces of the upper portions of the end wall and of the sidewalls. The 
upper wall 15 rests on the end face of the end wall 16 and braces the 
latter, as apparent from FIG. 3. The foot pedal 2 can be easily opened for 
repair purposes as a result of the twopart construction and detachable 
connection of the two parts. 
The restart arrestor 20 has a circuit 30 as shown in FIG. 5 including a 
relay 27 with a self-holding circuit 28 in which is located a switch 29 
that is actuated by the release button 21. The switch 26 of the switching 
device 19 lies in the circuit 30, which is connected to a source of power 
31. 
In order to actuate the apparatus equipped with the foot pedal 2, the 
release button 21 of the restart arrestor 20 is first pressed against 
spring force, thus closing the switch 29 in the self-holding circuit 28. 
The relay 27 is therefore energized, and the contacts 32, 33 are closed. 
The switch 29 remains closed as long as the relay 27 is energized. The 
switch 26 is then actuated to drive the motor 106, whereby the circuit 30 
is closed and the motor 106 is turned on. 
During a power failure, the relay 27 drops out, so that the contacts 32,33 
and the switch 29 are opened, whereby the release button 21 is returned 
under spring force to its starting position. When the problem is corrected 
and power is restored, the self-holding circuit 28 and the circuit 30 are 
opened because of the open contacts 32, 33, so that, when the switch 26 is 
closed, the motor is not turned on. Only after pressing the release button 
21 is the relay 27 energized and the contacts 32, 33 closed again, so that 
then also the circuit 30 is closed and the motor is turned on. 
In the illustrated embodiment, the foot lever 23 with the switch 26 is an 
on and off switch, i.e. the switch 26 remains closed after one depression 
of the foot lever 23. The foot lever 23 must then be pressed down again to 
open the switch 26. 
The foot lever 23 can also be a tipping switch which when pressed down 
closes the switch 26, and when released opens the switch again. The 
contact 33 is not absolutely necessary with such a construction. In this 
situation, the circuit 30 is not closed until after the foot lever 23 is 
pressed. The contact 33 however can also be provided in such a situation 
for additional safety, so that in any case, after a power failure, the 
circuit 30 can not be closed again until the restart arrestor 20 is first 
actuated. 
The restart arrestor 20 is easily accommodated in the housing 3 of the foot 
pedal 2 and wired with the switching device 19. The accommodation in the 
foot pedal 2 additionally has the great advantage that the manner of 
protection prescribed for the installation of electrical switching devices 
can be provided in a simple manner. Additionally, no changes of the 
apparatus itself are necessary, since the restart arrestor 20 is 
accommodated in the foot pedal 2. Furthermore, apparatus already being 
used can very simply be subsequently equipped with the restart arrestor 
20. For this purpose, it is only necessary to disconnect the connecting 
cable already provided with these foot pedals; this can generally be 
carried out by a layman, i.e. an individual who is not an electrician. The 
connecting cable 1 is then joined to the completely installed and wired 
foot pedal, and also to the restart arrestor 20, which is integrated and 
connected to the foot pedal. 
The embodiment of a foot pedal illustrated in FIGS. 6 through 8 is very 
similar to the embodiment of FIGS. 2 through 4. The only difference is 
that an emergency shutoff device 35 is also arranged in the upper 
receiving chamber 17 in addition to the restart arrestor 20. This 
emergency shutoff device 35 is provided with an operating or control 
element 36, which also projects outwardly through an opening 37 in the 
upper wall 5 of the housing 3. As shown in FIG. 6, the release button 21 
and the operating element 36 in the upper wall 5 of the housing 3 are 
located diagonally across from each other, resulting in a space-saving 
arrangement. The release button 21 and the operating element 36 can be 
pressed against spring force. 
Referring now to FIG. 9, the emergency shutoff device 35, which has two 
switches 38, 39 which are actuated in common by a plunger or push rod 
connected with the operating element 36, lie in the circuit 30 of the 
restart arrestor 20. In order to actuate the apparatus equipped with the 
foot pedal 2, the release button 21 of the restart arrestor 20 is pressed 
against spring force, whereby the switch 29 in the self-holding circuit 28 
is closed. The relay 27 is therefore energized, and the contacts 32, 33 
are closed. As long as the relay 27 is energized, the switch 29 remains 
closed. The switches 38, 39 of the emergency shutoff device 35 are 
likewise closed. To drive the motor 106 of the apparatus, the switch 26 is 
actuated by pivoting the foot lever 23, whereby the circuit 30 is closed 
and the motor 106 is turned on. 
So that the apparatus can be instantaneously disconnected from the electric 
circuit in case of danger, such as when the clothing of the operator 
catches in a thread-cutting machine, the plunger 40 is pressed by the 
operating element 36, whereby the switches 38, 39 are opened. As a result, 
the circuit 30 is interrupted, so that the motor 106 is immediately turned 
off. The relay 27 also drops out when the operating element 36 is pressed, 
so that the contacts 32, 33 and the switch 29 are opened, whereby the 
release button 21 is returned under spring force to its starting position. 
The emergency shutoff device 35 must be switched on again when the danger 
has been eliminated. For this purpose, the plunger 40 can be embodied with 
the operating element 36 as a mechanical switch which is held in the 
pressed-in position under spring force, and is held in the pulled-out 
position by clamping force. When the plunger is pulled-out, the switches 
38, 39 are closed. Preferably, the emergency shutoff device 35 is embodied 
in such a way that the plunger 40 remains in the pressed-in position after 
it is pressed in, so that the switches 38, 39 can no longer be closed by 
the plunger 40. The switches 38, 39 are electrically connected with a 
nonillustrated safety device which is disconnected when the plunger 40 is 
pressed. This safety device can be arranged on the apparatus itself, or at 
a location remote from the set-up site of the apparatus. The safety device 
must be reconnected in order to reconnect the emergency shutoff device 35, 
whereby the switches 38, 39 are closed, and the plunger 40 is returned to 
its starting position. Current can then flow again in the circuit 30. The 
self-holding circuit 28 and the circuit 30 are open because of the open 
contacts 32, 33, so that, even with a closed switch 26, the motor 106 is 
not yet turned on. The relay 27 is energized, and the contacts 32, 33 are 
closed, only after the release button 21 has been pressed, so that then 
the circuit 30 can also be closed, and the motor 106 can be turned on. 
The restart arrestor 20, independent of actuation of the emergency shutoff 
device 35, safeguards reconnection of the apparatus after a power failure 
and elimination of the problem. During a power failure, the relay 27 drops 
out, whereby the contacts 32, 33 and the switch 29 are opened in the 
manner described above. The switches 38, 39, however, are closed. If the 
problem is eliminated and current flows again, the motor 106 cannot be 
turned on again until the release button 21 is pressed, thus energizing 
the relay 27 and closing the contacts 32, 33 again. 
According to a further embodiment, only the emergency shut-off device 35 is 
accommodated in the receiving chamber 17 of the housing 3. The apparatus 
can be disconnected from the circuit in case of danger by this emergency 
shutoff device 35. As shown in FIG. 10, both switches 38, 39 of the 
emergency shutoff device 35, as well as the switch 26, which is actuated 
by the foot lever 23, lie in the circuit 30. 
With this embodiment too the circuit 30 is opened, by opening the switches 
38, 39, by pressing the plunger 40 by means of the operating element 36, 
so that the motor 106 is turned off. The switches 38, 39 of the emergency 
shutoff device 35 must be closed again in the manner described above to 
turn the apparatus on again. In contrast to the previous embodiment, the 
switch 26, and hence the circuit 30, can now be closed by the foot lever 
23, so that the motor is turned-on. 
The foot lever 23 with the switch 26 is an on-and-off switch in both of the 
previously described embodiments, so that the switch 26 remains closed 
after one depression or pressing-down of the foot lever. The foot lever 
must then be pressed again to open the switch 26. 
The foot lever can also be a tipped switch which when pressed down closes 
the switch 26, and when released opens the switch again. The contact 33 is 
not absolutely necessary with the embodiment of FIGS. 6 through 9. In this 
situation, the switch circuit 30 is not closed until the foot lever 23 is 
pressed. The contact 33 however can also be provided in such a situation 
for additional safety, so that in any case, after a power failure, the 
circuit 30 cannot be closed again until the restart arrestor 20 has been 
actuated. 
The restart arrestor and/or the emergency shutoff device 35 are easily 
accommodated in the housing 3 of the foot pedal 2 and wired with the 
switch device 19. The accommodation in the foot pedal has the advantage 
that the manner of protection prescribed for the installation of 
electrical switching devices can be provided in a simple manner. No 
changes are necessary on the apparatus itself, since the restart arrestor 
20 and/or the emergency shutoff device 35 are accommodated in the foot 
pedal. Thus, apparatus already being used can very easily subsequently be 
equipped with such a restart arrestor and/or such an emergency shutoff 
device. For this purpose, it is only necessary to disconnect the 
connecting cable already provided with these foot pedals; this can 
generally be carried out by a layman. The connecting cable 1 is then 
joined to the completely installed and wired foot pedal and the restart 
arrestor and/or emergency shutoff device which are integrated and 
connected to the foot pedal. 
With the embodiments according to FIGS. 6 through 10, the apparatus can be 
instantaneously disconnected from the electric circuit in case of danger 
either in addition to, or also independent of the presence of a restart 
arrestor. 
In place of a thread-cutting machine, other portable apparatus for 
machining tubular and/or rod-shaped workpieces or the like, or other 
electrical tools, can also be equipped with a foot pedal in the manner 
described above. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.