Press apparatus

A pressing device (1, 111), in particular for joining a pipe (23) with a press fitting (24), has at least two pressing jaws (17, 18, 21, 22, 122, 123, 124, 125, 126) and a drive (7) for moving the pressing jaws (17, 18, 21, 22, 122, 123, 124, 125, 126) or a part thereof relative to one another from an open position into a final pressed position, such that at least one sensor (36, 37, 38, 39, 40, 41, 42, 51, 151, 152) for sensing the final pressed position of the pressing jaws (17, 18, 21, 22, 122, 123, 124, 125, 126) is arranged in the region of the pressing jaws (17, 18, 21, 22, 122, 126), and such that an indicating device (43), which generates an externally perceptible indicating signal when the final pressed position is or is not reached, is associated with the sensor (36, 37, 38, 39, 40, 41, 42, 51, 151, 152).

The invention concerns a pressing device, in particular for joining a pipe 
with a press fitting, having at least two pressing jaws and a drive for 
moving the pressing jaws or a part thereof relative to one another from an 
open position into a final pressed position. 
It is known, in order to join pipes, to use sleeve-like press fittings that 
are made of plastic or metal. To produce a pipe joint, the press fitting 
is slid over the pipe ends and then radially compressed, both the press 
fitting and the pipe being plastically deformed. Pipe joints of this kind 
and the pertinent press fittings are known, for example, from DE-C-11 87 
870 and EP-B-0 361 630. 
Pressing of the press fitting and the pipe is accomplished with the aid of 
pressing devices such as are known in various embodiments, for example 
from DE-C-21 36 782, DE-A-34 23 283, EPA-0 451 806, EP-B-0 361 630, and 
DE-C-42 40 427. The pressing devices have at least two, and in some cases 
even more pressing jaws, at least a portion of which can be moved radially 
inward during the pressing operation to form a closed pressing space. A 
hydraulic piston, which can be acted upon by hydraulic pressure via a 
manually driven or electric motor-driven pump, is often provided as the 
drive to move the pressing jaws. 
The pipe joints described above are produced, in particular, when 
installing water-carrying pipework in buildings. It is obviously extremely 
important that the press fitting and pipe ends be compressed so as to 
guarantee absolute tightness. The material deformation must therefore be 
uninterrupted over the circumference of the press fitting. To achieve this 
result, the pressing jaws are displaced until their respective opposing 
pairs of end faces come into contact, or at least until only a slight gap 
remains between said end faces. 
To achieve this, the drive is displaced into its final position. The 
desired and predefined final pressed position of the pressing jaws is not 
necessarily, however, achieved thereby. The forces which occur lead to 
elastic deformations at the levers on which the pressing jaws sit or which 
are used to contract a pressing jaw ring. In addition, the pressing jaws, 
press fittings, and pipes are subject to tolerances which, if they add up 
unfavorably, mean that compression is insufficient when the final position 
of the drive is reached. In order nevertheless to be able to produce a 
leakproof pipe joint, the pressing jaws are acted upon by a pressing force 
which is designed, with the addition of a sufficient safety factor, so 
that in normal circumstances an adequate and therefore leakproof pressing 
is achieved. 
Problems can nevertheless still occur, and result in an incomplete 
pressing. For example, it is difficult to maintain a constant final force 
for the drive. Achieving the final force is in most cases the 
responsibility of a release member acting as switching member, for example 
a torque coupling for rotating drives, a pressure relief valve for 
hydraulic devices, and an overcurrent release for electrically driven 
devices. Since the release member does not measure the drive force 
directly, but rather measures a converted magnitude (torque, pressure, or 
current) which represents only a fraction of the magnitude of the final 
force, any inaccuracy in the manufacture of the release member, and any 
wear, can have major effects on the final force of the drive and thus 
ultimately on pressing quality. The latter is also influenced by the 
ambient temperature and operating temperature. A particular difficulty is 
that the change in the final force, due primarily to wear, proceeds 
gradually, and therefore remains unnoticed by the control system. 
A further reason for an incomplete pressing may lie in wear on the bearings 
for the transfer levers between the drive and the pressing jaws. This then 
causes an elongation of the pivot axes, with the result that in their 
final positions, the pressing jaws no longer constitute the desired 
contour, so that the predefined final pressed position is no longer 
reached. This again remains unnoticed by the control system. 
Lastly, crushing of the press fitting can also occur if material or 
immovably adhering dirt gets into the gap between the respective opposing 
end faces of the pressing jaws. This prevents said gap from being closed 
all the way into the desired final pressed position despite the fact that 
the final force is reached in the drive. The result is then a defective 
pressing, with the result that tightness cannot be guaranteed. 
It is therefore the object of the invention to configure a pressing device 
of the aforesaid kind in such a way that a substantially greater 
reliability can be achieved in the production of pipe joints. 
According to the invention, this object is achieved in that at least one 
sensor for sensing the final pressed position of the pressing jaws is 
arranged on at least one pressing jaw; and an indicating device, which 
generates an externally perceptible indicating signal when the final 
pressed position is or is not reached, is associated with the sensor. 
The principle of the invention consists in sensing the final pressed 
position of the pressing jaws substantially directly, i.e. at a point 
where falsification is practically ruled out, and then providing the 
operator, in a manner perceptible to him or her, with information as to 
whether the pressing jaws actually have or have not reached the final 
pressed position. 
In its most general form, the information consists in the fact that, 
depending on or whether or not the pressing jaws have reached the final 
pressed position, the pressing device experiences a change in state that 
is perceptible to the operator. Direct sensing of the position of the 
pressing jaws, and the information based thereon, ensure that the operator 
knows whether or not the pressing was sufficient. If the operator 
ascertains that the final pressed position was not reached, for example 
because too low a drive force was generated or because wear occurred in 
the drive and/or in the transfer levers, the operator can repeat the 
pressing operation with a new pressing device. 
With the approach as described above, the operator receives the information 
via an indicating signal. The indicating signal can be configured in any 
way, provided only that it makes perceptible a change in state at the 
indicating device. A visually perceptible indicating signal is 
particularly suitable for this purpose. An audibly perceptible indicating 
signal is also, of course, a possibility. If electrical current is 
available, the sensor can have a feeler which generates an electrical 
signal, and the indicating device can have a lamp which is electrically 
connected to the feeler. Instead, however, it is also possible to 
configure an indicating device so that it has a mechanical indicating 
member, which is coupled to the sensor in such a way that its position 
changes when the final pressed position is reached. The coupling can be 
purely mechanical or electromechanical. 
According to a further feature of the invention, provision is made for the 
indicating device to have an indicating memory which maintains the 
indicating signal even after the pressing jaws have moved toward the open 
position, the indicating memory having an externally actuatable canceling 
device. The indicating signal is thus maintained, regardless of the 
indicating signal, until it is canceled by manual action. This ensures 
that the operator receives the information regarding pressing quality. It 
may be advantageous in this context that the canceling device has an 
actuation lock which can overridden only with a tool. The tool can then be 
in the possession of a person who is responsible for inspecting the 
pressing device. 
The underlying principle of the invention can also be carried out by the 
fact that at least one sensor for sensing the final pressed position of 
the pressing jaws is arranged on at least one pressing jaw; and the sensor 
is coupled to the drive in such a way that the drive is automatically 
switched off by means of a shutdown device after the final pressed 
position is reached. With this embodiment of the principle, the operator 
receives the information as to whether the final pressed position has been 
reached via the fact that the drive is automatically shut down. If no 
automatic shutdown occurs, the operator knows that the pressing was not 
complete. The operator can then decide whether to continue or discontinue 
the pressing operation. The latter will be possible if the drive reached 
its final force. This embodiment of the principle of the invention can 
also be combined with the first embodiment, so that the operator 
additionally receives an indicating signal which informs him or her as to 
whether or not the final pressed position has been reached. 
The underlying principle of the invention can also be carried out by the 
fact that at least one sensor for sensing the final pressed position of 
the pressing jaws is arranged on at least one pressing jaw; and the sensor 
is coupled to the drive via a locking device in such a way that the drive 
can no longer be activated, if it has been switched off during a pressing 
operation, unless the sensor or sensors has or have sensed the final 
pressed position. 
In this instance the operator receives the information regarding the 
pressing quality only after the drive has shut down. If the drive can 
readily be started again, the operator can be certain that the pressing 
operation performed previously was correct, i.e. that the final pressed 
position was reached. Otherwise an attempt can be made to resume pressing, 
or--if this does not succeed--the pressing device must be replaced. This 
embodiment of the invention can once again be combined with the 
embodiments of the invention described above, so as to provide, in 
addition to the indication and/or the automatic drive control system, an 
additional guarantee against the continued use of a pressing device that 
is no longer suitable. 
Prefferably, the locking device should have an externally actuatable 
unlocking device so that, if the reason for the mispressing does not lie 
in the pressing device itself, the pressing device can be used for the 
production of further pipe joints. To ensure that this capability is not 
misused by the operator in cases in which the reason for the mispressing 
lies in a deficiency of the pressing device itself, it is advantageous to 
configure the unlocking device in such a way that it can be actuated only 
with the use of a tool. The tool can be kept in a location where an 
inspection of the pressing device can be performed. 
It is essential to the manner in which the invention achieves the object 
that the sensor senses the position of the respective pressing jaw 
substantially directly, i.e. without the interposition of levers or the 
like which connect the pressing jaws to the drive. For this purpose, the 
sensor can be arranged on a non-moving part of the pressing device in such 
a way that it senses the position of the respective associated pressing 
jaw, in particular its final pressed position. Alternatively thereto or in 
combination therewith, the sensor or one of the sensors can be arranged on 
one pressing jaw in such a way that it senses the position of the pressing 
jaw with respect to an adjacent pressing jaw. This can also be done by 
arranging the sensor or at least one of the sensors on two adjacent 
pressing jaws, in such a way that it senses the position of those pressing 
jaws relative to one another. This is preferably done so that the sensor 
or sensors is or are arranged in the region of the opposing end faces of 
two adjacent pressing jaws, so that the gap between said end faces is 
sensed. In many embodiments it is advantageous if several or all pairs of 
opposing end faces each have a respective sensor associated with them. 
If multiple sensors are provided in order to sense the final pressed 
position of the pressing jaws, they should be coupled to one another so 
that they emit a signal only if all the sensors have sensed the final 
pressed position. In this context, the signal can be used for all three 
embodiments of the principle of the invention, i.e. to generate an 
indicating signal, to shut down the drive, and/or to hold open the locking 
device for the drive. 
The basic principle of the invention can be applied to all pressing devices 
of the species cited initially. This also applies to an embodiment in 
which the pressing jaws sit on a pressing ring which has, in the region of 
an open closure point, coupling elements for the engagement of 
corresponding coupling elements of a closing device (cf. EP-A-0 627 273). 
The coupling elements on the pressing ring side can be moved together by 
means of the closing device to close the pressing ring, the sensor or at 
least one of the sensors being arranged in the region of the closing point 
and/or of the coupling elements on the closing device side. This latter 
arrangement is also one that is in the region of the pressing jaws as 
defined by the basic idea of the invention, if the coupling elements are 
in engagement. 
A wide variety of embodiments is possible for the sensor, in this case 
particularly all known and desirably applicable sensors for sensing the 
position of the pressing jaws. In particular, the sensor can have a 
movably mounted feeler which coacts with a stop against which the feeler 
arrives as the pressing jaws are closed. In this context, the feeler can 
be attached to one pressing jaw and the stop to the adjacent pressing jaw, 
in order to sense their position relative to one another. The stop can be 
the end face, located opposite the feeler, of the pressing jaw itself. A 
separate stop, which is adjustable in the movement direction of the feeler 
so as to allow precise alignment, is nevertheless preferable. In an 
advantageous embodiment, the feeler is coupled to a sensor which senses 
the positional change of the feeler. All sensors based on the principles 
of induction, eddy current, capacitance, magnetism, or resistance are 
possible here. Optical sensors, for example in the form of photoelectric 
barriers, are also possible, however. Pressure sensors or travel sensors 
can also be used. 
Even if the feeler is arranged on the pressing jaw itself, it is possible 
to arrange the sensor outside the pressing jaws if the feeler has a 
corresponding extension. This has the advantage that any electrical lines 
remain on the part that is fixed to the unit, thus facilitating, for 
example, replacement of pressing jaws. 
A fourth embodiment of the basic principle of the invention consists in 
providing, in the region of the pressing jaws, at least one locking device 
which, after the pressing operation has been initiated, prevents the 
pressing jaws from being opened back to the open position until the final 
pressed position has been reached. In this case the operator can 
recognize, based on whether or not the pressing device can be completely 
opened again after the pressing, whether the pressing quality was 
sufficient, i.e. whether the final pressed position of the pressing jaws 
was reached. In this context, the locking device is preferably 
mechanically configured, since this guarantees a high level of 
reliability. Electrically operating locking devices are also possible, 
however; the lock itself can be implemented by means of an electrically 
actuated interlock. It is understood that this means of achieving the 
object can also be combined with the other three embodiments of the 
principle of the invention in order to improve protection against 
continued use of a pressing device that is no longer working properly. 
The locking device preferably has an externally actuatable unlocking device 
so that the pressing device can be removed from the pressing point if the 
pressing jaws cannot, upon further pressing attempts, be moved into the 
final pressed position. This eliminates any disassembly of the pressing 
device. Here again, it is disadvantageous that the unlocking device cannot 
easily be activated manually, but rather that a tool is needed for the 
purpose. By having the tool in the possession of another person, this 
ensures that a "two-heads" inspection will be performed. 
The locking device(s) should each be attached to two adjacent pressing 
jaws, preferably in the region of two opposing end faces. 
The locking device can be configured in many ways. One possible mechanical 
solution is characterized in that the locking device has on the one side a 
locking member and on the other side a guide device into which the locking 
member engages, the locking member and/or guide device having locking 
elements which constitute a return lockout acting only in the opening 
direction, and the guide device having a diverting device which the 
locking member reaches only if the pressing jaws are in the final pressed 
position, and which then deflects the locking member into a return track 
which bypasses the return lockout. This locking device principle can be 
carried out in many ways. It offers a high level of security that the 
pressing device can be opened completely only if the pressing jaws have 
been moved into the final pressed position.

In the Figures, identical parts or those of identical function are labeled 
with the same reference characters in the various embodiments. 
Pressing device 1 depicted in FIGS. 1 through 4B has two T-shaped bearing 
plates 2, 3 which are arranged, when viewed from the front, exactly one 
behind another. A connecting pin 4 passes through the lower part of 
bearing plates 2, 3. Placed on said connecting pin 4 from both sides are 
support plates 5, 6 (front support plate 5 is omitted from FIGS. 1, 3A, 
3B, 4A and 4B), which belong to the drive labeled in its entirety as 7. 
Only their upper portion is depicted. Secured to their lower ends is a 
hydraulic cylinder (not depicted here), from which a piston rod projects 
upward. The upper end of the piston rod is equipped with a drive head 8 
that is configured in a fork shape at the top. Inside drive head 8, two 
drive rolls 9, 10 are mounted next to one another, freely rotatably about 
a horizontal axis. By means of the hydraulic cylinder, drive head 8 can be 
moved vertically in the direction of arrow F (and, of course, also moved 
back). Connecting pin 4 is of removable design, so that the entire drive 7 
can easily be taken out. 
In the upper region, bearing pins 11, 12, arranged at a distance next to 
one another, pass through bearing plates 2, 3. A pivot lever 13, 13 is 
mounted on each of bearing pins 11, 12 between bearing plates 2, 3. The 
two pivot levers 13, 14 are configured in mirror-symmetrical fashion. They 
have drive arms 15, 16 proceeding downward from bearing pins 11, 12, and 
jaw arms 17, 18 proceeding upward. Drive arms 15, 16 have drive surfaces 
19, 20 which are initially only slightly inclined from the horizontal, and 
then transition into a region oriented steeply upward. Semicircular 
recesses which constitute the contour of pressing jaws 21, 22 are shaped 
into the sides of jaw arms 17, 18 located opposite one another. 
FIG. 1 and 2 show pressing device 1 in the open position, in which drive 
head 8 assumes its lowest position in which it is not resting against 
drive arms 15, 16. Pressing device 1 is placed on a pipe joint so that it 
lies between pressing jaws 21, 22. The pipe joint has a pipe end region 23 
over which a press fitting 24 is partially slid. This is particularly 
evident from FIG. 2. Press fitting 24 has a cylindrical section 25 having 
a centrally located constriction 26 which acts as a stop for pipe end 
region 23. At the free ends, press fitting 24 has outwardly bulging 
annular beads 27, 28 into the inside of each of which an elastomeric 
sealing ring 29, 30 is set. Pressing jaws 21, 22 are located at the level 
of right-hand annular bead 28 in FIG. 2. 
For the pressing operation, the hydraulic cylinder (not depicted) is acted 
upon by hydraulic pressure via a corresponding pump so that the piston 
rod, together with drive head 8 mounted thereon, travels upward in the 
direction of arrow F (FIGS. 3A, 3B, 4A and 4B). Drive rolls 9, 10 thereby 
initially come into contact against the shallowly inclined sections of 
drive surfaces 19, 20. As upward travel continues, drive arms 15, 16 are 
spread apart, the result of which is that jaw arms 17, 18 approach one 
another and pressing jaws 21, 22 come into contact against annular bead 
28. As drive head 8 continues to move upward, the actual pressing 
operation begins, in which annular bead 28 and the immediately adjoining 
region of cylindrical section 25 are plastically deformed radially inward, 
pipe end region 23 also being plastically deformed radially inward in the 
last stage of pressing. In this context, drive rolls 9, 10--as visible 
from FIGS. 3A, 3B, 4A and 4B--travel into the region between drive arms 
15, 16 where drive surfaces 19, 20 are now at a very acute angle, i.e. are 
inclined very steeply with respect to one another. 
FIGS. 3A, 3B, 4A and 4B depict incorrect closing positions and the reasons 
for them; in both cases, complete pressing does not occur because pressing 
jaws 21, 22 do not reach their final pressed position. In the situation 
depicted in FIGS. 3A and 3B, material of annular bead 28 has been squeezed 
between the respective opposing pairs of end faces 31, 32 and 33, 34, as 
is evident in particular from the detail enlargement in the region of the 
lower pair of end faces 33, 34. This material prevents further pressing of 
press fitting 24, and does so (as shown by the position of drive head 8) 
at an early point in time. The amount of pressing is so small that the 
connection between pipe end region 23 and press fitting 24 is not sealed, 
i.e. is defective, even though drive 7 has exerted its maximum force. 
The situation according to FIGS. 4A and 4B shows the position of pressing 
jaws 21, 22--in this case without a pipe joint--when wear has occurred on 
bearing pins 11, 12 so that they exhibit an impermissible level of play. 
In the unloaded state (FIGS. 1 and 2), bearing pins 11, 12 assume the 
position drawn with dotted lines. When pressing jaws 21, 22 are moved 
toward one another as drive head 8 is moved upward, the center points of 
bearing pins 11, 12 are displaced outward, within the existing play and as 
a reaction to the forces thereby occurring, into the position drawn with 
solid lines. The result is that although pressing jaws 21, 22 come into 
contact with their upper end faces 31, 32, a gap 35 remains in the region 
of lower end faces 33, 34, as is particularly clear from the detail 
enlargement. This gap can reach a dimension such that in a pressing 
operation, insufficient pressing of press fitting 24 will occur in this 
region, so that the pipe connection is not tight in this region. 
Both types of mispressing, which can also result from different wear 
causes, are generally not noticed, or are noticed only after a number of 
mispressings have already been performed. To prevent this from happening, 
additional devices which will be evident from the Figures described below 
are provided according to the invention. In most cases, for reasons of 
clarity, drive 7 has in this context been taken off after removal of 
connecting pin 4. In addition, pressing jaws 21, 22 here are not shaped 
like segments of a circle, but rather are hexagonal in shape when closed. 
This is immaterial to the function of the additional devices, however, 
i.e. the latter are suitable for any desired contour of pressing jaws 21, 
22. 
In the exemplifying embodiment of FIGS. 5 through 8, a guide block 36, in 
which a feeler pin 37 is guided in axially movable fashion, is attached to 
left-hand jaw arm 17 at the level of lower end faces 33, 34. In a region 
of enlarged diameter, feeler pin 37 has two annular flanges 38, 39 
arranged at a distance from one another, which leave an annular groove 40 
between them. Left-hand annular flange 38 is acted upon, on the side 
facing away from annular groove 40, by a compression spring 41 which 
braces against a cover 42. With pivot levers 13, 14 in the open position 
shown in FIGS. 5 and 6, right-hand annular flange 39 rests against a stop 
in guide block 36. Above annular flanges 38, 39 and annular groove 40, an 
indicating pin 43 is arranged in a corresponding cylindrical channel. 
Indicating pin 43 has at the lower end an annular collar 44 which is acted 
upon in the direction of annular groove 40 by a compression spring. 
Indicating pin 43 projects outward from guide block 36 and is movable 
axially perpendicular to feeler pin 37. At the outer end, indicating pin 
43 has a further annular collar 46 with which it can be grasped manually. 
Arranged in stationary fashion in the region of the right-hand end surface 
34 of pressing jaw 22 is a stop block 48. It corresponds to feeler pin 37 
such that as pressing jaws 21, 22 close, feeler pin 37 arrives against 
stop block 48. 
Annular flanges 38, 39 on feeler pin 37 are arranged so that the axial 
extension of annular groove 40 is somewhat greater than the diameter of 
lower annular collar 44 of indicating pin 43. In the open position (FIGS. 
5 and 6), annular collar 44 rests with its underside on left-hand annular 
flange 38, so that it cannot drop into annular groove 40. In this 
position, feeler pin projects the farthest out of guide block 36. During 
the pressing operation, pressing jaws 21, 22 pivot with respect to one 
another in the closing direction (FIGS. 7 and 8). Shortly before the final 
pressed position is reached, the projecting end of feeler pin 37 comes 
into contact against stop block 48. As pressing jaws 21, 22 move farther 
in the closing direction, feeler pin 37 is pushed into guide block 36, 
with the result that annular flange 38 supporting indicating pin 43 is 
also displaced. This continues until annular flange 38 slips out of the 
region of annular collar 44, and indicating pin 43, with annular collar 
44, drops into annular groove 40. In this context, the individual parts 
are configured so that this cannot occur until pressing jaws 21, 22--as 
shown in FIGS. 7 and 8--have reached their final pressed position, thus 
ensuring that the pressing is correct. Since indicating pin 43 projects 
only slightly out of guide block 36, the operator can see immediately 
whether pressing jaws 21, 22 have actually reached the final pressed 
position, or whether an incomplete pressing has occurred. In the latter 
case, indicating pin 43 would remain in the initial position as shown in 
FIGS. 5 and 6. 
After pressing device 1 has been removed from the pipe joint, indicating 
pin 43 is once again pulled out against the action of compression spring 
45. This releases feeler pin 37, so that it is pushed by compression 
spring 41 back toward the opposing end face 34 against the internal stop. 
Pressing device 1 is then ready for another pressing operation. 
In the exemplifying embodiment as shown in FIGS. 9 and 11, guide block 36 
is rotated 90 degrees so that indicating pin 43 projects horizontally. 
Otherwise no modifications have been made. 
Additionally, however, there is secured to bearing plate 2 a Z-shaped 
locking bracket 49 whose free limb 50 engages in the movement region of 
indicating pin 43 when the latter is in the position pulled out of guide 
block 36. This position is visible in FIGS. 9 and 10. The outer annular 
collar 46 of indicating pin 43 is then located directly in front of limb 
50 of locking bracket 49. 
When the pressing operation is initiated, starting from the open position 
visible in FIGS. 9 and 10, annular collar 56 is moved against limb 50. 
Since the latter is of bendable configuration and is also--as is evident 
from FIG. 11--wedge-shaped on the side facing guide block 36, limb 50 is 
bent by annular collar 46 away from guide block 36, so that indicating pin 
43 can move past locking bracket 49. Subsequent pressing is accomplished 
in the manner already described with reference to the exemplifying 
embodiment shown in FIGS. 5 through 8. Pressing jaws 21, 22 can readily be 
opened when they have reached their final pressed position. In this case 
indicating pin 43 with its annular collar 44 has moved into annular groove 
40, and projects only slightly from guide block 46. It therefore does not 
collide with limb 50 of locking bracket 49 upon opening. If the pressing 
was incomplete, however, because pressing jaws 21, 22 did not reach the 
final pressed positions, and if indicating pin 43 has thus retained its 
initial position (FIG. 11), left-hand pressing jaw 21 can no longer pivot 
into its initial position since limb 50 is acting as a lock for indicating 
pin 43. A manual intervention is then necessary, either to bend locking 
bracket 49 aside or to push feeler pin 37 in sufficiently for indicating 
pin 43 to drop into annular groove 40. In this case, therefore, the visual 
indication by way of indicating pin 43 is combined with a locking device 
which allows pressing jaws 21, 22 to be opened into the open position only 
if either the final pressed position has been reached, or the locking 
effect of the locking device has been overridden by manual intervention. 
In the exemplifying embodiment according to FIGS. 12 and 13, a clearance 
sensor device 51 operating on the eddy-current principle is attached to 
right-hand jaw arm 18 at the level of the lower pair of end faces 33, 34. 
Said device has a coil bar 52 that is U-shaped in cross section, into each 
of whose U-arms 53, 54 an electrical coil is incorporated, in opposing 
fashion (not depicted). Coil bar 52 extends horizontally toward the 
opposing end face 33, in which a feeler plate 55 is guided displaceably in 
the longitudinal direction. It projects out of coil bar 52 toward the 
opposing end face 33. Arranged in coil bar 52 on the side facing away from 
end face 33 is a compression spring 56 which attempts to move feeler plate 
55 toward end face 33. 
Feeler plate 55 has a reference slot 57 whose extension in the axial 
direction of feeler plate 55 is on the same order as the smallest gap that 
may be expected between end faces 33, 34 in the event of a mispressing, 
i.e. if the final pressed position is not reached. In the direction toward 
the pair of end faces 33, 34, feeler plate 55 has, spaced away from 
reference slot 57, a window 58 whose side adjacent to reference slot 57 
constitutes a measurement edge 59. 
Located on left-hand jaw arm 17, opposite feeler plate 55, is a stop pin 60 
which is threaded into a retaining block 61 secured to jaw arm 17. Stop 
pin 60 can be axially adjusted via the threads in the through hole of 
retaining block 61 and on stop pin 60. Once the position has been found, 
it can then be immobilized with a locknut 62. 
With pivot levers 13, 14 in the open position (not depicted here), feeler 
plate is extended well out, and projects beyond the adjacent end face 34. 
During the pressing operation, feeler plate 55 comes in contact against 
stop pin 60 in a specific position and is pushed into guide housing 52 as 
pressing continues. Reference slot 57 thereby initially moves past the 
eddy-current coils, with the consequence that the damping resulting from 
feeler plate 55 is abolished and a signal amplitude is created which is 
taken as a reference. As feeler plate 55 is pushed farther in, a damping 
then occurs again because of the material of feeler plate 55 between 
reference slot 57 and window 58. As pressing is continued, measurement 
edge 59 then also arrives in the region of the eddy-current coils, so that 
the damping decreases again. 
With pressing jaws 21, 22 in the closed position achieved at the completion 
of pressing, the amplitude generated by reference slot 57 is compared with 
the amplitude effected by measurement edge 59. If the quantitative 
difference between the two amplitudes exceeds a predefined value, feeler 
plate 55 was not pushed far enough into coil bar 52, i.e. pressing jaws 
21, 22 did not reach their final pressed position. In this case a signal 
can be generated that is made visually perceptible, for example in the 
form of a lamp. This indicates to the operator that the pressing was 
incomplete. No visible indication is then given if the pressing was 
correct, so that the absence of a visible indication gives the operator 
the information that pressing jaws 21, 22 have reached their final pressed 
position. The signal state described above can be stored, so that any 
visual indication can be canceled only by manual intervention. This can be 
made even more difficult--thus prompting an inspection--if the indication 
can be canceled only by using a specific tool (special key). It is also 
possible, of course, to configure the circuit conversely, so that a 
visible indication is given only when the final pressed position is 
reached. If no such indication is given, the operator knows that a 
mispressing occurred. 
The result of the comparison of damping amplitudes can also be used for 
other purposes, in order to prevent the operator from performing 
additional mispressings for an even longer period. For example, in the 
event of an incomplete pressing, a signal can be given to a locking device 
for drive 7 which makes it impossible for drive 7 to start again. 
Provision can be made, in this context, for the locking device to be 
unlockable by manual intervention. In this context, unlocking can also be 
made more difficult by making it possible only with the aid of a special 
tool. 
In the exemplifying embodiment shown in FIGS. 14 and 15, a clearance sensor 
51 operating on the eddy-current principle is also used, its coil bar 52, 
U-shaped in cross section, again being secured to the outer side of 
support plate 5 of drive 7. The lower end of a transfer lever 63 projects 
into coil bar 52, transfer lever 63 once again having, in the region of 
coil bar 52, a reference slot 57 and a window 58 arranged at a distance 
from one another. 
The upper end of transfer lever 63 is secured to a feeler pin 64 which is 
suspended, pivotably about a horizontal axis, on a bearing pin 66 via a 
tab 65. In its outer portion, the feeler pin is surrounded by a 
compression spring 67 which attempts to pivot feeler pin 64 clockwise. 
Located once again on the left side is a stop pin 60 which is retained in 
a manner analogous to the exemplifying embodiment illustrated by FIGS. 12 
and 13. 
With pressing jaws 21, 22 in the open position (not depicted), feeler pin 
64 is pivoted clockwise sufficiently that it projects beyond end surface 
34, and so that reference slot 57 is located on the left side of the 
eddy-current coils in coil bar 52. When pressing occurs, the end face of 
feeler pin 64 comes into contact against stop pin 60. Further pressing 
causes a counterclockwise pivoting of feeler pin 64, so that first of all 
reference slot 57 moves past the coils in coil bar 52 and thus generates a 
reference signal, and as the operation proceeds, window 58 of measurement 
edge 59 comes into the influence region of the eddy-current coils. The 
comparison of damping amplitudes already described with reference to the 
exemplifying embodiment according to FIGS. 12 and 13 can then be 
performed; the possibilities described there for using a signal depending 
on the particular closed position can be utilized again here. 
The two exemplifying embodiments according to FIGS. 17 through 20 on the 
one hand, and FIGS. 21 and 31, share the feature that the additional 
device for ensuring that the pressing jaws 21, 22 reach their final 
pressed position are configured as locking devices which allow pressing 
jaws 21, 22 to be opened without manual intervention only if pressing jaws 
21, 22 have first reached their intended final pressing position. 
In the exemplifying embodiment according to FIGS. 16 through 20, a locking 
device 68 is provided, part of which is a catch strut 69 that is 
suspended, pivotably about a horizontal axis 70, on left-hand jaw arm 17 
at the level of the lower pair of end faces 33, 34. Catch strut 69 
projects into a lock housing 71 which is mounted on jaw arm 18, pivotably 
about a horizontal axis 71a. Catch strut 69 is displaceably guided in lock 
housing 71 in a guideway 72. At that end, a catch 74 having a downwardly 
projecting catch tooth 75 is mounted, pivotably about a horizontal axis, 
via a pivot pin 73. Attached at the top of the free end of catch 74 is an 
actuation pin 76 which projects out of lock housing 71 through an opening 
77 provided there. Catch 74 is of bendable configuration, so that its free 
end can be bent away from guideway 72, toward opening 77, by actuation pin 
76. Also secured to actuation pin 76 is a tension spring 78 (indicated 
only schematically with dot-dash lines), the other end of which is 
attached to jaw arm 18. 
Guideway 72 is of straight configuration, and has in its end region a catch 
step 79. Guideway 72 is raised at the end, and transitions into a curved 
diversion track 80 proceeding at right angles from it. From this, a return 
track 81 proceeds obliquely back toward guideway 72; in addition, return 
track 81 is not milled in as deeply as guideway 72. 
In the open position (FIGS. 16 and 17), the free end of catch strut 69 is 
located in the inlet region of guideway 72. Catch tooth 75 thus rests on 
guideway 72 with a preload. Upon closure of pressing jaws 21, 22, catch 
strut 69 is pushed farther into lock housing 71. Despite the force 
proceeding from tension spring 78, catch 74 cannot enter return track 81 
because the latter is not as deep as guideway 72, so that a step is formed 
in the connection from guideway 72 to return track 81. As pressing jaws 
21, 22 approach closer, catch tooth 75 slides over catch step 79 (FIGS. 18 
and 19). Catch step 79 then prevents pressing jaws 21, 22 from being 
brought back into the open position after an incomplete pressing in which 
pressing jaws 21, 22 did not reach the final pressed position. This is 
possible only after catch tooth 75 has been lifted by actuation pin 76 
sufficiently far away from guideway 72 that it can be moved back over 
catch step 79. A manual intervention is thus required for this, giving the 
operator the certainty that a mispressing has occurred. 
With pressing jaws 21, 22 in the final pressed position, catch 74 reaches 
the end of guideway 72. There it can pivot, under the tensile force of 
tension spring 78, into diversion track 80 (FIG. 20), and enters return 
track 81 (shown with dashed lines in FIG. 20). In this case pressing jaws 
21, 22 can be opened without manual intervention; catch tooth 75 slides 
via return track 81 back into guideway 72, and after pressing jaws 21, 22 
open, it once again reaches the position shown in FIGS. 16 and 17. After 
removal of pressing device 1, a further pressing operation can then be 
performed. 
FIG. 21 shows a pressing device 1 having a different locking device 82 
which bridges the gap between end faces 33, 34. Its more detailed 
configuration will first be explained with reference to FIGS. 22 and 23. 
Locking device 82 has an elongated shaped part 83 which is pivotably 
suspended via a pivot pin 84 (FIG. 21) on right-hand jaw arm 18. In the 
direction of the opposing end face 33, shaped element 83 extends in a fork 
shape with two fork arms 85, 86 arranged at a distance from one another 
and running parallel, thereby bridging the gap between end faces 33, 34. 
Suspended on the left-hand jaw arm 17 via a pivot pin 87 is a clamping 
block 88 which fits into in the open space between fork arms 85, 86 in 
mutually guided fashion. A spring rod 89, which at the free end has a 
catch 90 directed toward shaped part 83, is clamped in clamping block 88. 
As the plan view shows, catch 90 is wider than spring rod 89. 
In the right-hand region, shaped part 83 has a guide groove 91 
corresponding to the width of catch 90. Mounted above guide groove 91 is a 
slider plate 92 which braces against shaped part 83, since it is wider 
than guide groove 91. It has a retaining flange 93 into which a stop screw 
94 (depicted only in FIGS. 22 and 23), which extends horizontally, is 
threaded. It passes through an opening 95 in a stop web 96 which is part 
of shaped part 83. A stop nut 97 is located externally on stop screw 94. 
Said stop nut 97 limits the ability of slider plate 92 to move toward 
catch 90. Slider plate 92 is forced in that direction by two tension 
springs 98, 99. 
Slider plate 90 has a T-shaped slot 100. In the region adjacent to 
retaining flange 93, said slot 100 is as wide as guide groove 91 and catch 
90. In the region farther away from them, the width is reduced to slightly 
more than the width of spring rod 89, slot 100 continuing to the end of 
slider plate 92. 
Located below slider plate 92 is an S-shaped leaf spring 101 which is 
secured to the bottom of guide groove 91 and rests under a preload against 
the underside of slider plate 92. 
In the initial position with pressing jaws 21, 22 open, catch 90 is braced, 
under the preload of spring rod 89, against shaped part 83 (FIGS. 22 and 
23). Slider plate 92 is in the position remote from stop web 96, stop nut 
97 resting against stop web 96. As pressing jaws 21, 22 close, clamping 
block 88 and shaped part 83 slide within one another; catch 90 arrives 
against slider plate 92 and displaces it in the direction of arrow H 
(FIGS. 24 and 25). As pressing jaws 21, 22 close further, catch 90 slips 
over the edge of guide groove 91 located there, so that catch 90 fits 
completely into guide groove 91. Since all that is then located above 
shaped part 83 is spring rod 89, whose width is less than that of slot 90 
in slider plate 92, slider plate 92 moves under the influence of tension 
springs 98, 99 back into its initial position (FIGS. 26 and 27). Catch 90 
is then trapped in guide groove 91 by slider plate 92. As the operation 
continues, catch 90 is displaced in guide groove 91, thereby pushing leaf 
spring 101 downward onto the bottom of guide groove 91 (FIGS. 28 and 29), 
until catch 90 is located beneath the widened portion of slot 100. Since 
the width of slot 100 there is somewhat greater than that of catch 90, and 
since leaf spring 101 is stronger than spring rod 89, catch 90 is pivoted 
upward by leaf spring 101 (arrow I, FIGS. 30 and 31). In this context, the 
position of slider plate 92 is set, based on the adjustment using stop nut 
97 (FIGS. 22 and 23), in such a way that catch 90 can be pushed upward 
through the widened section of slot 100 only if pressing jaws 21, 22 have 
reached their final pressed position. 
Pressing jaws 21, 22 can now be opened again; catch 90 slides onto the 
outer side of slider plate 92, assisted by bevels at the transition from 
the widened section of slot 100 into the narrowed section (FIGS. 32 and 
33). When pressing jaws 21, 22 reach the open position, catch 90 slides 
back down away from slider plate 92, and then assumes the position evident 
from FIGS. 22 and 23. Another pressing operation can then be performed. 
If an incomplete pressing occurs, catch 90 does not completely reach the 
widened section of slot 100 in slider plate 92. Pressing jaws 21, 22 can 
only be opened to the point where catch 90 strikes against the end of 
guide groove 91. The operator then knows that a mispressing has occurred. 
For complete opening of pressing device 1, slider plate 92 must then be 
removed. 
Pressing device 111 depicted in FIG. 34 has as the pressing tool a pressing 
ring 112 that is constituted by five curved pressing jaw carriers 113, 
114, 115, 116, 117. Pressing jaws 113 through 117 are joined to one 
another via articulating pins 118, 119, 120, 121, and carry a respective 
pressing jaw 122, 123, 124, 125, 126. Pressing jaws 122 through 126 are 
mounted, movably in the circumferential direction, on pressing jaw 
carriers 113 through 117. 
A closure gap 127 is located between the two lower pressing jaw carriers 
113, 117 and 122, 126. Closure gap 127 is bridged by a coupling device 128 
which has two coupling tabs 129, 130, left-hand coupling tab 129 being 
arranged, via an articulating pin 131, at the free end of left-hand lower 
pressing jaw carrier 113, while right-hand coupling tab 130 is articulated 
at the free end of right-hand lower pressing jaw carrier 117. Coupling 
tabs 129, 130 are joined to one another in articulated fashion via a 
coupling pin 134. Coupling bolt 134 is removable, thus making it possible 
to open pressing ring 112 wide in the region of closure gap 127, so that 
it can be placed around a press fitting. After placement, the two coupling 
tabs 129, 130 are once again joined to one another so that pressing ring 
112 can no longer drop down. 
Associated with pressing ring 112 is a closing device 135 which is depicted 
only schematically here. Closing device 135 has two substantially T-shaped 
bearing plates 136, arranged at a distance behind one another, between 
which two closure levers 140, 141 are arranged pivotably by means of 
articulating pins 138, 139. Closure levers 140, 141 each have lower lever 
sections 142, 143 and upper lever sections 144, 145. Upper lever sections 
144, 145 have recesses, oriented opposite to one another, as coupling 
elements. These are adapted to the articulating pins 131, 132 on which 
coupling tabs 129, 130 are articulated. Lower lever sections 142, 143 have 
drive surfaces 148, 149 oriented opposite to one another. A pair of 
rollers, which can be displaced vertically as part of a drive device (not 
depicted here) in the form of a hydraulic cylinder, can be introduced in 
known fashion into the space between drive surfaces 148, 149. For this, 
the drive device is suspended via a pin on bearing plates 136, 137, the 
pin being insertable into opening 150. 
For a pressing operation, the two lower lever sections 142, 143 are brought 
together manually so that the two upper lever sections 144, 145 are spread 
apart. Closing device 135 can then be placed onto pressing ring 112 in 
such a way that recesses 146, 147 are located opposite articulating pins 
131, 132. By moving the rollers into the initially narrow space between 
lower lever sections 142, 143, the latter are spread apart. Recesses 146, 
147 thereby grasp articulating pins 131, 132 and bring them closer 
together. As a result, pressing ring 112 is drawn together, making closure 
gap 127 smaller so that the pressing space enclosed by pressing jaws 122 
through 126 becomes smaller. This continues until the end faces of 
pressing jaws 122 through 126 come into mutual contact. In the process, 
the press fitting and the pipe end inserted into it are plastically 
deformed. To remove closing device 135 from pressing ring 112, the 
procedure is reversed. 
A sensor 151 (depicted only symbolically) is attached in the region of 
closure gap 127 to the two opposing side of pressing jaw carrier 113, 117. 
Said sensor is adjusted so that in the defined final pressed position, its 
two opposing parts butt against one another and thereby generate an 
electrical signal which can then be used for an indication. By way of the 
indication, the user learns that the final pressed position has been 
reached. Instead of the arrangement on pressing ring 112, an arrangement 
on closing device 135 is also possible, specifically in the region of 
recesses 146, 147 in this case. This sensor 152 has the same function as 
sensor 151. 
It is understood that the embodiments evident from FIGS. 5 through 15 are 
also possible for sensors 151, 152. They can also be combined with locking 
devices that are apparent from FIGS. 17 through 33.