GB2064394A - Oleodynamic torque wrench - Google Patents

Abstract

An oleodynamic torque wrench, for fastening nuts of leaf spring clamps or U-bolts of a motor vehicle, comprises a hydraulic driving motor on a wheeled carriage which operates, through a transmission drive (10, 11, 12), a rotary head or wrench (16) to be coupled with a nut or a bolt head. Control means (28, 29) for the pressure of the power fluid is provided in the feeding system of the hydraulic motor, to control the torque applied to the nut. The wrench may be in the form of a gun with the hydraulic motor built in, the gun being connected to the wheeled carriage. <IMAGE>

Description

SPECIFICATION Oleodynamic torque wrench The present invention relates to an oleodynamic torque wrench, that is an apparatus for the unscrewing and tightening of nuts or bolts, in particular the nuts for fastening the leaf spring clamps or U-bolts of a motor vehicle.

This apparatus is especially suitable to be used in heavy motor vehicles, wherein the torques to be applied to the nuts, both for the unscrewing and their tightening, are of high values. This problem is important in particular in connection with the nuts for fastening the mounting clamps of a motor vehicle leaf springs.

The tightening and unscrewing of nuts and bolts have been carried out manually, with the obviously resulting inconveniences, until motordriven devices have been designed to avoid manual strains of the operator.

These devices, although have afforded some advantages, such as a reduction of the working time, still show however remarkable inconveniences in connection with the solidity and the safety of the nut tightening.

In fact the most serious problems, which are to be faced when nuts are applied are rather related to the tightening of the nuts than the unscrewing thereof. This is due to the fact that conventional prior art devices do not provide for a suitable control of the force intensity applied to a nut, whereby the consequent tightening may be insufficient or excessive. In the first instance there are present, as it is clear, conditions of unsteadiness in the connection zone, which are emphasized in the specific case of motor vehicles wherein the connections undergo sensible stresses of substantially vibratory nature.

In the second case the connection is also unsteady, but for a different reason. This is because the force applied to the nut may cause dangerous stretches or cracks to be formed, which in turn may give rise to the failure of one or more of the joined pieces. It is clear that this drawback is extremely dangerous in case of motor vehicles.

A first type of known apparatus comprises a driving electric motor that operates a rotary head to be applied to the nut to be tightened. This apparatus, having a three-speed variator, has the serious inconvenience that the force intensity is a function of the power required to release the nuts when the three-speed variator is positioned at the minimum speed of rotation (maximum torque value), while each of the other two speed limits the tightening torque to a value which is substantially unknown and cannot be adjusted according to the diameter of the screw. Apart from these two values any tightening is obviously unsecured or excessively tight.

It is the object of the present invention to provide an apparatus for the tightening and unscrewing of nuts or bolts, in particular an oleodynamic torque wrench for the fastening nuts to be used in connection with the leaf spring clamps or U-bolts of a motor vehicle.

According to the invention there is provided an oleodynamic torque wrench apparatus for unscrewing and tightening nuts, in particular the nuts for fastening the leaf spring clamps or U-bolts of a motor vehicle, which comprises a driving motor for the actuation through a transmission drive of a rotary wrench head to be coupled to the nut for its screwing, wherein the driving motor is a hydraulic motor having a feed circuit to which adjustable control means are connected for controlling the pressure of the motor feeding fluid, whereby the resulting torque is varied.

Torque wrenches according to the invention overcome or at least substantially reduce the abovementioned inconveniences, at the same time rendering it possible, in particular during the fastening operation, to apply a torque that is strictly necessary to the tightening of a nut with a dynamometric force which is appropriate to the screw diameter.

Since the operation of the apparatus is reversible as will result from the following description, a torque wrench according to the invention can clearly be used also for the release of nuts or bolts by applying, if necessary, the maximum torque value to cause them to be unscrewed.

One apparatus according to the invention comprises an oleodynamic supply-station communicating with an oleodynamic motor which, through a transmission drive, operates a rotary head or wrench to be coupled with a nut for its screwing or unscrewing. An adjustable control means is provided on the feed circuit for controlling pressure of the fluid which enters the oleodynamic motor in order to vary the torque produced by the latter.

An oleodynamic torque wrench apparatus according to the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side view of the oleodynamic torque wrench apparatus; Figure 2 is a top plan view of the apparatus; Figure 3 is a rear-side view of the apparatus; Figure 4 is a side view showing a constructional variation of the apparatus; Figure 5 is a top plan view of said variation; and Figure 6 is a rear-side view of the variation.

Referring to the drawings, in Figures 1-3 the oleodynamic torque wrench apparatus of the invention comprises, on a frame 1, an oleodynamic supply-station 2 being provided with a suitable finning 3 for its cooling.

The oleodynamic supply-station 2 is operated by a motor pump 4, that is a known unit being comprised of an electric motor associated with a pump.

The oleodynamic supply-station 2, through an electrically driven hydraulic distributor 5, feeds a hydraulic motor 6 which, as shown in Figure 3, is positioned at the lower portion of the frame 1.

This figure shows two pipes 7, 8 from the distributor 5 for reversing the rotation direction of the motor 6. A third pipe 9 is also represented, which serves as a draining for the hydraulic motor 6.

A known speed reducer 10 is provided on the output shaft of the hydraulic motor 6 and consists for example of a known reduction bevel gear whose output shaft, mounted within a sleeve 11 being fixed to the frame 1, is at right angles to the shaft of the hydraulic motor 6.

An extension sleeve 12 has one end fixed to the outer end of the sleeve 11 and is provided to this effect with a cylindrical fitting member 13 on which a setscrew 14 and an adjustment pin 1 5 are radially screwed.

A rotary articulated head or wrench, generally designated 16, is mounted at the other end of the extension sleeve 12 and is adapted to be applied to the nut to be fastened having a complementary shape thereto. Only for the sake of brevity of representation the head or wrench 16 shown at Figure 1 is a male wrench, while the one shown at Figure 2 is a female or socket wrench.

The head or wrench 1 6 is rotatable around an axis perpendicular to the longitudinal axis of the shaft of the speed reducer 10 and may be displaced in a plane perpendicular to the latter axis upon unscrewing the setscrew 14 and the pin 15.

This allows to position the head 16 according to the location of the nut to be fastened.

The onnection between the head 16 and the shaft of the reduction gear 10 may be made in whichever manner, not shown, such as by means of a pair of bevel gears mounted within a substantially cylindrical body 17 bearing the head 16.

The apparatus according to the invention, in particular the sleeve 11, is supported by a pair of wheels 18, which provide for its movement up to positioning at the various operative locations. The sleeve 11 is supported by means of a fork member 19 having two arms 20 positioned laterally of the sleeve 11 and pivotedly mounted at one end to a pin 21 thereof. At the opposite end each arm 20 extends into another arm 22 which forms, with the first arm 20, a substantially V-shaped member The second arms 22, which extend laterally of and above the sleeve 11, are provided with holes 23 for the insertion and fastening of a cross-bar 24 which is constructed to support the sleeves 11, 12 as a whole as they are brought to the raised position illustrated in phantom at Figure 1.

The wheels 18 mounted for rotation on an axle 25, are connected by a cross-bar 26 between the common ends of the arms 20, 22.

A means for controlling the feeding fluid pressure is connected to the hydraulic motor feed circuit.

A means of this type is not illustrated in detail, being known per se and consists of a control valve. Figure 2 shows the control knob 27 of the above-mentioned means.

A pressure gauge 29 on the feeding circuit of the hydraulic motor 6, allows to select the pressure of the operating fluid and thereby the torque applied by the apparatus onto the nut to be tightened. Advantageously, as in particular shown in Figure 3, the pressure gauge 29 will be provided with a graduated scale 30 for an easier reading from an operator. The scale 30 is in Kg.m, such as up to 208 Kg.m. The graduation in Kg.m instead of in Kg/m2 is because the pressure gauge 29 can be considered as a torque meter. Thus, to each diameter of the screw a well determined value of the torque value will correspond. The torque value is obtained from a suitable dynamometric table applied to the apparatus. In this table each screw diameter corresponds to a well determined torque value.

The apparatus is also provided, at one of its side wails, with a control panel having the necessary push-buttons and control knobs. By 32 there is indicated the start push-button of the apparatus, by 33 an electric three-position switch for controlling clockwise and counterclockwise rotations of the hydraulic motor by means of the distributor 5, as well as for stopping the hydraulic motor and by 34 the push-button for the stop of the apparatus.

In a known manner there is provided a filter 36 between the supply station 2 and the hydraulic motor 6.

An electric cable 37 is wound on a pulley 38 rotatably mounted on the frame and provides for the connection of the apparatus to the supply mains socket. A handle 40 is provided at the rear side of the apparatus for its movement. Obviously the pulley 38 can be omitted and the electric cable 37 can be wound directly on the handle 40.

Making reference to Figures 4 6 a different embodiment of the apparatus according to the invention is now described. This embodiment is substantially the same as the one abovedescribed, the only difference being that the feeding lines of the fluid from the hydraulic supply station to the hydraulic motor are of the flexible type, not rigid. The head or wrench 16, as well as the hydraulic motor, are mounted on a gunshaped support 41 which can be easily grasped by hand. The gun 41 can be shaped as the head of a lapping machine.

In Figures 4 6 similar elements as in Figures 1-3 are indicated by the same reference numerals, although the mutual position relationship of some of them has been modified for constructive and functional reasons only.

Therefore the description of such elements is here omitted.

The hydraulic motor arranged within the gun 41 is connected to the hydraulic supply station in a known manner through flexible hoses in a sheath 42 wound on a reel 43 rotatably mounted on the frame 1. The gun 41 is provided with a control switch 44 by which the operator, directly on place, actuates the hydraulic motor and thus the head or wrench 16. According to the preceding embodiment this purpose was achieved by means of an additional switch 33a having the same functions as switch 33, positioned near the head 16.

Finally it should be noted that in the construction variation, the speed reducer 10 with the associate shaft and thereby the sleeves 11, 12 are omitted. The hydraulic motor has been arranged within the gun 41 and thus cannot be seen in Figures 4-6.

Furthermore the frame 1 in this case is directly supported by four wheels 18, thus eliminating the above-described support unit comprising the fork 1 9 and the associate bearing pins. The hydraulic supply station, in the alternative embodiment, has been positioned at the inside of the frame 1, whereby it is not visible.

From the foregoing the advantages of the described apparatus are self-evident, in particular with respect to the screwing and tightening of the nuts, no special cautions being necessary for the unscrewing thereof. When unscrewing it will be sufficient to preset the operation of the hydraulic motor at the maximum value of the pressure. On the contrary for the screwing it will be always possible to apply a torque value which is strictly necessary to obtain a correct and stable fastening of the nut.

Claims (4)

1. An oleodynamic torque wrench apparatus for unscrewing and tightening nuts, in particular the nuts for fastening the leaf spring clamps or U-bolts of a motor vehicle, which comprises a driving motor for the actuation through a transmission drive of a rotary wrench head to be coupled to the nut for its screwing, wherein the driving motor is a hydraulic motor having a feed circuit to which adjustable control means are connected for controlling the pressure of the motor feeding fluid, whereby the resulting torque is varied.

2. An apparatus according to claim 1 wherein the transmission drive between the hydraulic motor and the rotary head comprises a reduction gear with a driving shaft housed in a sleeve having a first section fixed to the apparatus frame and an extension for a different positioning in two perpendicular planes, one of which passing through the rotation axis of the rotary head.

3. An apparatus according to claim 1 or 2, wherein the rotary head is mounted on a support suitable to be manually gripped, the hydraulic motor being arranged within the gun and being connected to the hydraulic supply station through flexible hoses.

4. An oleodynamic torque wrench apparatus substantially as above-described and illustrated in the annexed drawings.