EP1404491B1 - Pressure-operated power screwdriver having a measuring section - Google Patents

Abstract

The power screwdriver comprises a functional part (11) with a housing (14) through which a shaft (17) passes. The shaft (17) is provided with a toothing (18), into which a ratchet lever of the functional part (11) engages. A splined shaft toothing (20) of the shaft (17) has an insertion recess (21) that changes into a cavity (22). The wall of the cavity (22) is provided with a torsion sensor (23) and forms a measuring section (25) that is located in the area of the shaft (17) covering the housing (14). A torsion measurement is effected in the measuring section (25). Due to the measuring section (25) being located in the area of the shaft covering the housing (14), the shaft (17) is relatively short whereby enabling it to be used under tight spatial screwing conditions involving a low head height above the screw. The power screwdriver is additionally provided with an angle measuring device (33) whereby torque and angle of rotation can be simultaneously provided and can be used for controlling and recording.

Description

The invention relates to a pressure-operated hydraulic or pneumatic power wrench with a drive part and a functional part, wherein the functional part has a shaft driven by a ratchet lever, which has a driving device, and with a measuring section determining the torsion element.

A hydraulic power wrench of this type is known from DE 296 07 207 , In this power wrench, the shaft extends transversely through the housing of the functional part. Outside the housing, a torsional measuring section is provided on the shaft. In this measuring section, a torsion sensor in the form of multiple strain gauges is mounted on the shaft. The torsion sensor forms an electrical resistance arrangement whose resistance is dependent on the torsional moment. At the end of the shaft is a driving device, which can be coupled with a tool or with a screw head. This power wrench with measuring cell makes it possible to measure the torsional moment acting on the screw, whereby the tightening torque can be determined directly at the screw connection.

The invention has for its object to provide a pressure-operated power wrench with drive part, functional part and a measuring section, which has small dimensions in the axial direction of the screw and thus at low head height (above the screw) can be used.

The solution of the stated problem is defined by claim 1. After that, the measuring section is formed in a cavity of the shaft or a hollow shaft connected therewith in a rotationally fixed manner. Here, the torsion sensor of the measuring section is attached to the inner wall of the cavity. There is no space for the torsion sensor on the outside of the shaft. This can overlap with a toothing, which is provided on the outside of the shaft and on which engages the ratchet lever. Thus, the measuring section of the shaft does not require any additional length. Added to that in the Cavity of the torsion sensor is protected from external influences is housed and that an additional encapsulation of the measuring section is not required.

On the housing, an angle sensor may be provided which determines the angle of rotation of the shaft. Here, in addition to the direct torque measurement inside the device, a direct rotation angle measurement also takes place at the same time. The integration of the angle sensor in the power wrench, the flat construction is not significantly affected, so that the direct measurement can be performed even in extremely confined spaces. It has been found that the combination measurement of torque and angle of rotation allows the most accurate tightening process for highly sensitive screw connections.

The angle sensor is preferably arranged in a cap which encloses the one end of the shaft. In this way, there is a protection of the angle sensor from mechanical damage and contamination. On the other hand, the lateral extension of the housing can be kept relatively small by the cap. Through the cap, a data transmission can take place, either by means of slip rings or by wireless transmission.

In the following, embodiments of the invention will be explained in more detail with reference to the drawings.

Fig. 1

eine schematische Seitenansicht einer ersten Ausfüh- rungsform des Kraftschraubers, teilweise geschnitten,

Fig. 2

einen Schnitt entlang der Linie II-II von Fig. 1,

Fig. 3

einen Schnitt durch eine nicht zur Erfindung gehörende zweite Ausführungsform, bei der der Messabschnitt außen an der Welle angeordnet ist,

Fig. 4

einen Schnitt durch eine dritte Ausführungsform, bei der der Messabschnitt im Innern der Welle angeordnet ist,

Fig. 5

einen Schnitt durch eine nicht zur Erfindung gehörende vierte Ausführungsform, bei der die Welle mit der Schlüsselnuss über eine Zwischenwelle gekoppelt ist,

Fig. 6

eine fünfte Ausführungsform, bei der der Messabschnitt in einem rohrförmigen Teil der Schlüsselnuss angeordnet ist,

Fig. 7

eine sechste nicht zur Erfindung gehörende Ausführungsform, bei der der Messabschnitt außen an einem rohrförmigen Teil der Schlüsselnuss an- geordnet ist,

Fig. 8

ein siebtes Ausführungsbeispiel, bei dem der Messab- schnitt in einem rohrförmigen Teil der Schlüsselnuss angeordnet ist, die ihrerseits mit einer Zwischenwelle verbunden ist, und

Fig. 9

eine nicht zur Erfindung gehörende ähnliche Version wie Fig. 8, jedoch mit außen an- geordnetem Messabschnitt.

Show it:

Fig. 1

1 is a schematic side view of a first embodiment of the power wrench, partially in section,

Fig. 2

a section along the line II-II of Fig. 1 .

Fig. 3

a section through a not belonging to the invention second embodiment, in which the measuring section is arranged on the outside of the shaft,

Fig. 4

a section through a third embodiment, in which the measuring section is arranged in the interior of the shaft,

Fig. 5

a section through a fourth embodiment not belonging to the invention, in which the shaft is coupled to the key nut via an intermediate shaft,

Fig. 6

a fifth embodiment in which the measuring section is arranged in a tubular part of the key nut,

Fig. 7

a sixth embodiment not belonging to the invention, in which the measuring section is arranged on the outside on a tubular part of the key nut,

Fig. 8

a seventh embodiment, wherein the measuring portion is arranged in a tubular part of the key nut, which in turn is connected to an intermediate shaft, and

Fig. 9

a not belonging to the invention similar version as Fig. 8 , but with externally arranged measuring section.

The power screwdriver after the Figures 1 and 2 has a drive part 10 and a functional part 11. The drive part 10 is replaceably attached to the functional part 11. The driving part 10 includes a hydraulic cylinder (not shown) in which a piston is slidable. The drive part 10 has on the cylinder housing 12 a pivotable connection device 13 for hydraulic hoses.

The functional part 11 has a housing 14, which here consists of two assembled housing halves 14a and 14b. In the housing 14 there is a cavity 15, in which a (not shown) ratchet lever of the drive member 10 can be pivoted back and forth. In a transverse bore 16 which extends through the housing 14, a shaft 17 is rotatably mounted. This shaft 17 has in the interior of the housing 14 has a circumferential toothing 18, in which engages a toothing of the ratchet lever. This way everyone gets Hub of the drive member 10, the shaft 17 is rotated about its axis by a certain angular amount. Then the return stroke of the ratchet lever, in which the shaft 17 is not taken.

The shaft 17 has at one end a driving device 20, which is designed here as a key nut 40 and forms a Einsteckausnehmung 21 of hexagonal cross-section. The Einsteckausnehmung 21 is located in the protruding from the housing 14 part of the shaft 17 and extends into the housing 14 into it. In this way, the protruding from the housing part of the shaft can be kept relatively short. The insertion recess 21 merges into a cavity 22 which is formed in the shaft 17. On the peripheral wall of the cavity 22, the torsion sensor 23 is in the form of strain gauges, which are glued to the peripheral wall. Between the Einsteckausnehmung 21 and the cavity 22 is an inwardly projecting annular flange 24 which protects the torsion sensor 23 against external interference. The cavity 22 forms an axial extension of the Einsteckausnehmung 21. When the Einsteckausnehmung 21 is placed on a nut to be rotated, the cavity 22 can accommodate the protruding from the nut screw shank. Therefore, the insertion recess 21 may have a relatively small axial length. Alternatively, the Einsteckausnehmung can also serve to receive the shaft of a key nut or be designed as a square opening.

The cavity 22 is adjoined by a frusto-conical transition 26, which opens into a receiving space 27 in which a data transmission element 28 is contained. From the torsion sensor 23, a cable channel 29 extends to the data transmission element 28. The data transmission element 28 is, for example a slip ring assembly which connects an external cable 30 to the torsion sensor 23 which is rotatable with the shaft 17. Alternatively, the transmission can also be wireless. The cable 30 leads to a cable connection 31 (FIG. Fig. 1 ), which is provided on a cantilever arm 32 of the housing 14 and to which a control or measuring device can be connected.

The hydraulic power wrench is further equipped with a rotation angle measuring device 33. This has a code disk 34 which is fixed on the Einsteckausnehmung 21 remote from the end of the shaft 17, and an angle sensor 35 which responds to the lines of the code disk 34 and thereby determines the angle of rotation of the shaft. The angle sensor 35 consists of a fork-type photoelectric sensor into which protrudes the code disk 34 projecting radially from the shaft.

The angle sensor 35 is contained in a cap 36 which is mounted on a part of the housing 14 and fastened with screws 37. The cap 36 surrounds the rear end of the shaft 17 facing away from the Einsteckausnehmung 21 and at the same time forms a protective housing for this shaft end and the angle measuring device 33. From the angle sensor 35 leads a cable 38 to the cable terminal 31, so that both the torsion sensor 23 and the Angle sensor 35 is electrically accessible to the cable connector 31.

Under constant measurement of the torsional moment of the shaft 17 and the angle of rotation of this shaft can be an exact control of the operation of the power wrench and in particular a targeted achievement of the desired Schraubanzugsmoments. It is also possible to store the data measured during a screw tightening process and store them in a memory, to be able to document the tightening process later. This is especially important when tightening safety-relevant screws.

In the following embodiments, the drive part 10 and the functional part 11 are each formed in the same manner as described with reference to FIG FIGS. 1 and 2 has been described. In each case, the power transmission from the shaft to the key nut is different, as will be explained below.

In the embodiment of Fig. 3 the shaft 17 is arranged in the housing over its entire length. On the one half of the shaft, it has a driving device 20a in the form of a splined toothing, which engages with a corresponding external toothing of a key nut 40. The key nut 40 has a hexagonal insertion recess 21 in a widened head 41. The head 41 extends partially into the housing 14. At de head 41, a hollow shaft 42 connects. This hollow shaft has an outer wedge toothing which engages with the driving device 20a of the shaft 17. Between this external spline and the head 41 is a measuring section 25 with a torsion sensor 23, which is arranged sunk in the annular groove 42 of the hollow shaft. The drive torque is transmitted from the shaft 17 to the hollow shaft 42 and from there via the measuring section 25 to the head 41 of the key nut 40. In this variant, even a part of the head 41 is recessed in the housing 14, so that the axial length of the power wrench can be kept extremely short.

The embodiment of Fig. 4 corresponds to that of Fig. 3 , but with the difference that the torsion sensor 23 is arranged on the inside of the hollow shaft 42. electrical Connecting cables can be easily guided through the hollow shaft to the torsion sensor.

In the embodiment of Fig. 5 the shaft 17 projects out of the housing 14 towards the rear end. On the protruding part, it is provided on the inside with a spline toothing 20 a, which engages with a corresponding driving device 20 a on the outside of an intermediate shaft 44. The intermediate shaft extends to the front through the housing 14 and it has in its front region an internal spline 45 and in its rear region a bearing bore 46th

The key nut 40 has a head 41 with a Einsteckausnehmung 21. At this head, a hollow shaft 42 connects, on which a splined portion is provided, which engages with the spline 45 of the intermediate shaft 44. The hollow shaft 42 is followed by a hollow shaft section 47, which is mounted in the bearing bore 46.

In the area between the two splines 20a and 45 is the measuring section 25, with the torsion sensor 23 mounted in an outer groove of the intermediate shaft 44.

According to the embodiment Fig. 5 In the intermediate shaft key nuts 40 different key widths can be used, even the largest key widths are possible.

The embodiment of Fig. 5 can also be modified so that the torsion sensor 23 is contained on the inner wall of the intermediate shaft 44 in a recess.

Fig. 6 shows an embodiment in which the key nut 40 is connected to a hollow shaft 42 which engages in an inner driving device 20a of the shaft 17. The shaft 17 extends across the width of the housing 14, but does not substantially surmount this. The key nut 40 forms with the hollow shaft 42 a structural unit, which can be pulled out of the shaft 17 in total. The measuring section 25 is located on the keyed nut 40 in the area between the insertion recess 21 and the hollow shaft 42. From the torsion sensor 23, electrical wires 48 extend through the hollow shaft to a data transmission element 28, which operates in the same way as in FIG Fig. 2 is arranged, but here is located inside the hollow shaft 42. The power wrench is equipped with a rotation angle measuring device 33 which has a code disk 34 seated on the hollow shaft 42 and a housing-fixed angle sensor 35.

The embodiment of Fig. 7 is different from that of Fig. 6 only in that the torsion sensor 23 is arranged on the outside of the measuring section 25. Through the hollow shaft 42 performs a bore 46 for carrying the coming of the torsion sensor cable 23 into the interior of the hollow shaft.

Fig. 8 shows an embodiment in which the key nut 40 is extended with a hollow shaft 42 which includes a measuring section 25, wherein the torsion sensor 23 is arranged in the interior of the hollow shaft 42. The hollow shaft 42 is connected to an intermediate shaft 49, which engages in an inner driving device 20 a of the shaft 17. Through the intermediate shaft 49, the cable coming from the torsion sensor 23 passes through to emerge at the rear.

The embodiment of Fig. 9 is different from the one of Fig. 8 only in that the torsion sensor 23 is arranged on the outside of the measuring section 25. From there, a bore 46 leads into the interior of the hollow shaft 42.

Claims (6)

1. A pressure-operated power wrench comprising a drive part (10) and a functional part (11) having a housing (14) that includes a ratchet lever driven by the drive part (10), said ratchet lever driving a shaft (17) that extends transversely through the housing (14) and comprises a coupling section (20; 20a), said power wrench comprising a measuring section (25) measuring the torque, characterized in that the measuring section (25) is formed at a cavity (22) of the shaft (17) or of a hollow shaft (42) connected to the shaft for rotation therewith.
2. The power wrench according to claim 1, characterized in that the cavity (22) immediately follows an insertion recess (21) of the coupling device (20).
3. The power wrench according to claims 1 or 2, characterized in that an angle sensor (35) detecting the rotational angle of the shaft (17) is provided at the housing (14).
4. The power wrench according to claim 3, characterized in that the angle sensor (35) is arranged in a cap (36) enclosing one end of the shaft (17).
5. The power wrench according to one of claims 3-4, characterized in that the angle sensor (35) cooperates with a code disc (34) fastened on the end of the shaft (17).
6. The power wrench according to one of claims 1-5, characterized in that a data transmission element (28) is arranged at the end of the shaft (17).

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