PRE-CALIBRATED MANUAL TORQUE SCREWDRIVER

Field of application

The present invention relates to a pre-calibrated manual torque screwdriver whose pre- calibration device is contained within the handle. It consists of a plurality of thin cylindrical sectors for individual and modular pre-calibration, which are arranged mutually side-by-side coaxially and are each provided with a central female mating seat in order to mate with a corresponding number of male seats provided on the outer surface of the shanks which can be inserted longitudinally in the handle, are interchangeable and are provided, at one end, with the shape suitable to work with the seat formed on the head of the screw to be screwed in or loosened.

Different types of shanks and end shapes suitable to mate with the heads of screws are matched by different lengths of the male mating seats (having for example a hexagonal cross- section), and therefore they will mate simultaneously with one or more cylindrical calibration modules contained in the handle, thus producing a very specific torque (for screwing or unscrewing).

The technical problem of the tightening torque of screws with a screwdriver or appropriate wrenches is known. The use of a screwdriver in fact currently varies among different operators and the tightening torque is determined in relation to the individual strength, so there is no guarantee of perfect execution of the operation according to the technical standards that correspond to the type of screw.

Therefore, most of the time the step for tightening the screws does not occur according to the most elementary safety standards, for example in replacing and locking the inserts of tools on the tool holders or milling machines in general, for chip-forming (chipping) machining, or even in the aeronautical and/or aerospace sector.

The present invention solves the cited problem, providing a prepared and complete tool, which therefore does not require the operator to perform manual calibrations on the spot; it is instead sufficient to use the stem provided with the tip suitable for the screw, which ensures the exact torque for that specific type of screw.

Background art

We started from the assumption that in mechanical chip-forming (chipping) machining one uses tools with interchangeable inserts which are fixed mechanically by means of specific

screws currently known as Torx and Torx Plus, in sizes which vary in nos. 6-7-8-9-10-15-20 or other shapes.

These screws, in order to be managed, must be identified in their size, and after choosing the relevant screwdriver among the many, the operator can perform tightening with forces which are not determined by a general rule, since each operator entrusts his own sensitivity and experience, which of course varies from one operator to another.

Alternative solutions, such as fixed and adjustable torque screwdrivers, are commercially available and have disadvantages: screwdrivers of the fixed type, which can be monolithic or with an interchangeable blade, most of the time are uneconomical, since once the blade is worn it is necessary to throw away also the handle that contains the mechanism; screwdrivers of the fixed type but with an interchangeable blade allow replacement of said blade once it is worn, and therefore are slightly more advantageous than the preceding case, having in addition the severe drawback of possible accidental swapping with other blades which have similar dimensions but different technical characteristics. For example, if one inserts by mistake the Torx 15 blade in the handle that accommodates the Torx 6 blade, one obtains the torque related to Torx 6 on the Torx 15 tip, which is not the one prescribed by the technical standards.

Furthermore, various other types of manually used screwdriver with torque devices are known in the background art.

United States invention patents (US 4,238,978 and US 6,832,533) are known. The first one describes a T-shaped screwdriver handle with a torque device which can be adjusted directly by the operator by turning said handle, modifying the position of a split conical cam which is actuated with a snap action and is subjected to the action of two tangential springs with balls arranged at right angles to the axis of the screwdriver. The shank is fixed in the handle and is a single shank; its end is adaptable to different tips. This technical solution for providing a torque device in the handle of the screwdriver does not ensure the exact torque in relation to the type of screw. The operator must in fact know the various torques for the individual screws and must then adjust the handle to the correct position by moving the split conical cam which determines the attainment of the exact torque.

The second patent instead provides technically a traditional screwdriver handle in which the torque is adjusted by screwing or unscrewing the handle itself with respect to a single coupling of the universal type which is suitable to accommodate the tips of the screwdriver. In this case also, the experience of the operator in knowing the torque in relation to the type of screw to be tightened, and in therefore preparing said handle for this purpose, is needed. Therefore, the disadvantages and possible drawbacks in providing an incorrect torque are evident, and accordingly there is no assurance and guarantee of safety in the correct use of the

tool.

The prior patent of the proprietor of the present patent (UD2005A000050 with international extension WO 2006/105920) is also known which overcame the known disadvantages by providing a handle of a torque screwdriver which was pre-calibrated during manufacture and therefore did not require operator interventions to adjust the torque in relation to the type of screw to be tightened or loosened. Inside the handle there were modular rings with a torque function arranged mutually side-by-side and each provided with multiple seats which were tangent with respect to the internal bush and provided with balls subjected elastic springs with a force adjusted by suitable small screws.

Said balls act simultaneously on the internal bush, determining thereon the desired torque. Therefore, the action of multiple individual modular rings arranged side-by-side and coaxially produces a sum of individual torques which is equal to the desired torque. Each modular ring can be used in its pre-calibrated torque action or can be unused: this is possible by inserting longitudinally, through the central seat of the internal bush which is coupled in rotation by the action of the tangent balls, an elongated shank which has, on its outer surface, the mating seat (for example of the hexagonal male type), mating perfectly with the internal seat of each individual bush. As the mating length between the outer male surface of the shank changes, one or more pre-calibrated modular rings contained in the handle are affected and therefore different combinations of torques are determined. The shank has, at its end, the tip suitable for specific screws and at the same time a different length of the part affected by mating with the internal bushes so as to accordingly determine a different torque as provided by the technical standards.

The same patent cites a similar technical solution, replacing the side-by-side rings with tangential balls and springs, with equivalent side-by-side devices with radial teeth interposed with Belleville springs and compressed together within the handle. In this manner, a specific torque is provided; if said torque is exceeded, the affected components rotate freely. In this case also, a series of shanks or tips with a shaft suitably machined to determine the desired mating between the stem and the torque elements is used.

The advantages of the pre-calibration of the torques have been achieved by associating different shanks (for machinings related to the mating seats) for each type of screw (different shapes and dimensions). Ultimately, the tool is composed of a handle which contains internally a plurality of pre-calibrated side-by-side modular rings and a series of different shafts which can be associated therewith by longitudinal insertion and have different end shapes and different mating seats in the opposite side.

However, although this tool solves the drawbacks observed on the subject, it has been found to be rather complicated and laborious to manufacture, and therefore, in order to make it

industrially and commercially interesting, it has been thought to simplify it, using the same pre- calibration principle associated with interchangeable shanks which can be inserted in the handle itself of the screwdriver, in order to provide mass-production with the technologies of mechanics and of the plastics sector.

Summary of the invention

The aim of the present invention is to provide a torque screwdriver with pre-calibrated manual handle which can be associated, by insertion, with a plurality of elongated interchangeable stems which have coupling shafts which are particularly contoured and machined in mutually different manners in relation to the variation of the type of tip suitable for screwing or unscrewing different screws. Thereby, the following particular technical characteristics are highlighted:

- the handle is equipped with the pre-calibration torque device of the multiple type and does not require calibration or adjustment by the operator, since this operation is performed during the construction of the handle itself;

- the handle is suitable to accommodate and work with a plurality of side-by-side torque modules and of screwdriver rods and shanks, the latter being machined particularly in a longitudinal direction in relation to the type of end shape. The length that can be inserted in the handle is identical for all the stems and is machined so as to have an appropriate length for mating with the respective female seats of the bushes of the various torque modules. It varies depending on the type of tip for different types of screw, thus determining different and appropriate torques. The length of the stem in the part of the tip can be identical for all types or can vary depending on the requirements of operation. The mated shanks can be inserted and extracted longitudinally from the front part of the handle and are of the interchangeable type;

- the possibility to recognize the various types of shank in relation to the type of screwdriver tip, using colors and/or icons and/or numbers for each size,

- the possibility to use the recognition principle cited above also for the heads of the screws to be tightened or loosened and/or proximate to the supporting points of said screws, on tool holders or on the tools themselves and/or on parts of machines or devices;

- simplification in the construction of the torque device constituted by a plurality of coaxial torque units or modules which are pre-assembled and pre-calibrated, providing the modules also by using plastic material by molding in order to reduce costs and simplify the step for their assembly and calibration;

- optimizing the production of the handles containing the pre-calibrated torque devices, ensuring their reliability over time with a competitive overall cost;

- the possibility to pre-calibrate the individual torque modules, each with identical or different tangential forces according to the requirements or the various combinations of tension needed in order to comply with the technical standards required in relation to the type of shape;

- the possibility to form along the shank, in the regions for mating with the internal parts of the individual torque modules, appropriate lengths of mating seats having various geometric sectional configurations which obviously correspond to those of the internal bushes;

- the possibility to provide torque units or modules which can be arranged side by side within the handle with an identical or different number of tangential seats which act on the internal bushes suitable to accommodate and adjust the elastic springs that act on balls or cylindrical rollers;

- the possibility to use in an active condition all or a smaller number of the seats for the tension springs provided on the individual torque modules in order to obtain the desired torque;

- a screwdriver with a dynamometer device for tightening or loosening screws with pre- calibrated and guaranteed torques which is easy and traditional in its use by any operator, including non-expert ones.

Disclosure of the invention

The aim and objects of the invention are achieved according to the characteristics of the main claim and/or of any other claim cited in this patent text by providing a pre-calibrated manual torque screwdriver which contains, within the handle, the dynamometer device which can be mated and associated with a series of different shanks which can be inserted as needed from the front part of the handle in order to be used to screw or unscrew the screws, by imparting an appropriate torque according to the technical standards.

According to the present invention, the handle of the screwdriver, which has a traditional or anatomical shape, contains the torque device, which cooperates in coordination with a series of shanks which are provided with the tips suitable for screws, which can be inserted from the front part and are interchangeable. Said shanks can be of various length and cross-section, but the part that mates with the handle has an identical length and a different machining from one shank to another. This occurs because each shank has a different tip suitable to work with a specific shape or head of a screw having various technical characteristics (different thread diameters) and therefore needs a different and appropriate moment of torque. This difference is enhanced in the part mated with the pre-calibrated device of the handle and is achieved by providing one or more male mating seats (for example having a hexagonal cross- section) with a different length which is suitable to mate with the torque device within the handle, provided in the form of a female shape having a suitable cross-section. The parts that are

not affected by the mating are slightly modified.

Furthermore, the shank of the screwdriver can of the monolithic type, i.e., a contoured tang for insertion in the handle and a single or double tip equipped in a fixed manner so as to work on specific screws, or also possibly of the complex modular type, having only the tang contoured suitably for insertion in the handle provided with a tip which is interchangeable in relation to the geometric contour of the shape on the screw on which one is to work.

Instead, according to another version of the present invention, the modular torque device fitted within the handle can be different and can be constituted by a plurality of unitary, independent and coaxial elements, which are arranged mutually side by side and are separated by a thin washer. Each of these elements is locked rigidly to the container, preventing their rotation. Each module has, at the center, a bush which is free to rotate and has, at the center, a coaxial hole which reproduces a female mating seat (for example a hexagonal one, but it may have any geometric shape), while along the outer surface it has parallel seats which are equidistant from the central seat and have a semicircular cross-section. Such grooves are numerically identical or greater than the recesses provided on the torque module, and these last recesses accommodate suitable rollers or balls and springs. The recesses provided on each torque module are for example six, but their number can be different. They are arranged equidistantly on a plane which is perpendicular to the central axis and are inclined with respect to the central axis and are inclined with respect to the tangency between the module and the central bush. An elastic spring arranged from the outside inward (with a force suitable for the purpose) and a cylindrical roller arranged in position toward the internal tangency are inserted within each rectilinear recess. The action of the individual elastic springs on the rollers of each module determines a combined thrust on the external grooves of the central bush, since each roller partly mates against the grooves of the central bush, preventing its rotation in both directions. This total action of the rollers produces a torque, i.e., the sum of the forces (of the springs) by their lever arm. This prevents the rotation of the internal bush, unless a rotation action is applied thereto which overcomes the torque created by the individual springs and moves the rollers backward, thus allowing its rotation.

Each modular torque element has a given thickness and therefore acts on a similar length of the shank if it is provided with a mating seat. Multiple unitary modules arranged side by side within the handle determine a different combination of torques: from a minimum one (a value which corresponds to the value provided by the individual module) to a maximum one (related to the sum of the individual values of all the modules).

Of course, the torque modules can be all identical or can also have different technical characteristics, determining identical or different torques.

As already mentioned earlier, the various interchangeable shanks also have a different machining of the parts mated to the internal bushes, so that a different length of the shank-bush coupling also determines a different torque, since one or more torque modules are affected.

Ultimately, one obtains for each type of screwdriver stem a different and appropriate torque which complies with the relevant technical standards. Thereby, no intervention of the operator is needed as regards its adjustment, since the calibrations of the individual torque modules are performed during the construction of the handle and last throughout the life of the tool.

Furthermore, the torque screwdriver allows to have a pre-calibrated torque which is higher during unscrewing than during screwing; this is achieved by means of a tangent inclination of the tensioning device (elastic spring and sliding roller) with respect to the perpendicularity of the center of rotation of the rotating central body or bush.

In another preferential solution of the present invention, the torque module of the type which can be arranged side by side within the handle of the screwdriver can be provided, instead of by means of delimited recesses (by plastic molding) with contact at one end of the elastic spring and toward the inside with the roller, by means of rectilinear sliding seats, which are again perpendicular but are of the through type, in order to allow to position therein a roller (internally), an elastic spring (in an intermediate position) and an adjustment screw (externally).

In another preferential solution of the present invention, it is possible to use a ball instead of the cylindrical roller in providing the modular torque device.

Said screwdriver with a handle provided with a torque device which is of the multiple type (since it is formed by a plurality of side-by-side and independent unitary modules) finds an interesting application in the field of the interchangeability of plates made of hard and/or sintered metals on multiple tools such as mills and the like, which require, for obvious safety, an assurance of the locking and tightening torque of said plates on the central containment body, and also in the high-technology sector, in the aeronautical and aerospace sector and in the construction of scientific and sanitary devices and instruments, where a high performance of the manual tool is required which is capable of ensuring with certainly a pre-calibrated tightening torque for screwing the screws and/or a higher one during unscrewing.

Description of the drawings

This characteristic and others of the present invention will become better apparent, by way of prefered but non-limiting example in the accompanying eight drawing sheets, wherein:

Figure 1 is a perspective view of the screwdriver complete with the shank fitted on the handle;

Figure 2 is a longitudinal sectional front view of the screwdriver of the preceding figure, illustrating the individual torque modules contained within the handle;

Figure 3 is a front view of seven screwdriver shanks of the type with an end shape and provided with the mating tang made in seven different types which are contoured for different torque performances;

Figure 4 is a front view of the cover of the torque module, highlighting its peripheral and internal machinings suitable to mate with the module, forming a single disk-like body to be arranged side by side with respect to other similar ones;

Figure 5 is a side view of the cover according to the preceding figure;

Figure 6 is a perspective view of the cover of the preceding two figures;

Figure 7 is a side view of the machined disk-like element which constitutes the torque module; by mating with the cover of the preceding figures it forms a complete individual unit and can be arranged side-by-side with respect to other similar ones;

Figure 8 is a front view of the element of the preceding figure, illustrating the recesses for accommodating the elastic springs which are arranged on a plane which is perpendicular to the central axis, and the seats for the movement of the cylindrical rollers, which are parallel to said axis;

Figure 9 is a perspective view of the machined disk-like element according to the two preceding figures, fllustrating the recesses and seats for the rollers and the internal protruding parts which will mate with the cover element shown earlier;

Figure 10 is a side view of the internal bush which will mate with the central part of each complete torque module;

Figure 11 is a front view of the internal bush of the preceding figure;

Figure 12 is a perspective view of the internal bush of the two preceding figures, illustrating the equidistant longitudinal hollows on the outer surface and the hexagonal female mating seat for the tang of the various shanks;

Figure 13 is a front view of a second different torque module composed monolithically, with six holes for accommodating the springs of the type which is perpendicular to the central axis and inclined tangentially to the longitudinal central hole, clearly illustrating the longitudinal seats for the cylindrical rollers;

Figure 14 is a side view of the torque module of the preceding figure, shown partially in cross-section;

Figure 15 is a perspective view of the torque module according to the preceding figures;

Figure 16 is an exploded perspective view of a screwdriver complete with the torque devices, each composed of two modular elements;

Figure 17 is an exploded perspective view of a screwdriver complete with the torque devices, each composed of an element which is formed monolithically.

According to the invention, and in accordance with a first embodiment, the screwdriver handle 1 with pre-calibrated torque device contained inside the handle is suitable for tightening series of screws of various sizes by using suitable and interchangeable stems 2, of the single type (having a single end provided with a screwdriver tip) and machined particularly with variously positioned mating seats 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8 in the part of the tang that has a hexagonal cross-section, i.e., the part that is inserted in the front part of the handle and mates with the various internal torque modules.

The invention relates to a handle 1 which contains internally a plurality of disk-like torque devices arranged side by side and at right angles and coaxially with respect to the longitudinal axis of the handle (in this case five are drawn, but they can be in any number), suitable for pre-calibrated tensioning.

The handle 1 , which is provided hollow and made of metallic and/or plastic material, has a front perforated bush 1.1 (which can also be made of synthetic material, for example Teflon or equivalents) in which the shank 2 is inserted from the tang end and is provided, at the other end, with the tip suitable to mate with the head of the screw to be screwed or unscrewed. Said handle is closed at the rear by a hemispherical cover 1.2 with a screw.

As shown in Figure 2, the handle 1 is elongated and the stem 2 inserted axially therein is locked in position by virtue of the end mating in the seat 4 of a retention ball 6 which is subjected to the force of the spring 7 which is adjusted by means of a small screw 8 for containment in the respective seat obtained within the end cover 1.2. Five individual coaxial, cylindrical individual unitary torque modules are inserted side by side within the cylindrical handle and are kept pressed against each other by the end cover 1.2 and by a sealing rubber gasket 21. Each torque module is formed in turn by a body 13 and by a disk-like cover 12, which mate with each other. The body of the module 13, in the internal part, has a series of six seats or recesses 15 (their number can be changed in any case in relation to the type of cross-section of the stem being used), which are mutually equidistant and lie on a plane which is perpendicular with respect to the central axis, where a through hole 17 is provided in order to allow the passage of the tang of the shank of the stem 2. The recesses 15 have a direction which is inclined with respect to a diameter which is coaxial with respect to the axis of the through hole and are designed so that each one contains an elastic spring 11 of suitable thrust force which is directed toward the internal part of said module. At one end of said recesses 15, toward the internal part, there are seats 19 which are connected for sliding and containment of the cylindrical rollers 10

and are provided at right angles to the recesses of the springs and have, in the internal part, toward the central hole, a partially free surface so as to make a corresponding amount of lateral surface of the rollers contained therein protrude. Centrally, the body of the cylindrical module is extensively hollow, leaving a thin base wall for containment, and is perforated with a through hole 17 at the center. The central space must be used to accommodate an internal bush 9, which is preferably made of synthetic material, which is free to rotate about its own axis and which has, along its lateral surface, six equidistant hollows 20, which partially form the contact seat for the rollers 10; the internal part has a female through mating seat of the hexagonal type 22 and of course said cross-section can be different in its shape and dimensions in relation to the type of seat formed on the tang of the shank 2. Said mating seat 22 is used to connect the part of the tang of the shank 2 to the body of the torque module by means of the rollers 10, which partially make contact with the seats 20 of the bush 9.

The body of the torque module 13, once pre-calibration has been completed, by inserting in each recess 15 the corresponding elastic pusher spring 11 and in the seats 19 the roller 10, the rollers being subjected to the thrust of the respective springs toward the central part in partial contact with the seats 20 of the bush 9, which also is inserted in a central part, is closed with the disk-like element 12 acting as a cover, with a central through hole 17, and is hollow in the central part 16 in order to accommodate part of the internal bush 9 and partly the seat of the rollers 10. The two parts 12 and 13, together with the internal bush 9 and the springs 11 and the cylindrical rollers 10, formed the pre-calibrated torque module.

Both the disk-like element 12 and the body 13 have, on the outer surface, in a longitudinal direction (which is parallel to the central axis), three through grooves 14 arranged at 120°. Said grooves are meant to lock the torque module as a whole to the internal body of the handle 1, so as to avoid its rotation. The body of the handle in fact can have teeth which protrude inward, are longitudinal and rectilinear and arranged at 120° if the handle is produced with the method of molding thermoplastic material made of plastic or light alloy, in order to lock the modules within the handle once they are arranged mutually side by side. Moreover, said grooves 14 can be used to lock the modules also by passing through them thin rods 5 which lock against the body of the handle upon closure with the end cover 1.2 of the handle 1.

The handle of the screwdriver 1 contains internally, in this example, five pre-calibrated, independent, side-by-side and coaxial torque modules; at this point, if a shank 2 is inserted from the front part of the handle 1.1, its mating tang is particularly machined and contoured 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, and in this manner the mating length of the shank with the internal bush or bushes 9 is determined in order to affect one or more pre-calibrated torque modules, thus determining a total torque which is suitable for that type of screwdriver shape. The part of the

tang of the shank having a hexagonal cross-section in fact mates with a similar female seat 22 provided in the internal bush 9 of one or more modules and is subjected to the force of the respective springs 11 which act on the rollers 10 which determine as a whole the desired torque.

When the screwing torque, determined by one or more pre-calibrated torque modules, is exceeded, the internal bush or bushes 9 affected by the mating between them and the shank tend to rotate freely. This occurs when the screwing force applied to the handle exceeded the total thrust forces of the pre-calibrated springs 11 on the respective cylindrical rollers 10 which act on the hollows 20 of the bushes 9. The rollers tend to retract into their seat because they are moved by the internal bush 9, which is rigidly coupled to the stem 2, thus allowing its free rotation and therefore also the rotation of the entire handle 1.

The inclination of the forces of the springs with respect to the tangency of the internal bush 9 determines as a whole a pre-calibrated total moment of torque for screwing and determines a higher one for unscrewing.

The drawings show a second example of embodiment of the invention, which consists of a different manner of constructing the pre-calibrated torque module. It is in fact built as a single element 23 shaped like a cylinder with a central hole which has three hollows 26 arranged at 120° on its outer surface in order to allow its locking (prevention of rotation about its own axis) within the body of the handle. Said module has, on a plane which is perpendicular to the central axis, six radially equidistant holes 24 every 60°, which start externally from the lateral surface and are inclined so as to be almost tangent to the longitudinal central through hole. Each one of said holes 24 ends with an internal perpendicular seat 25, with a longitudinal direction, which is wide enough to allow the sliding and accommodation of a cylindrical roller. The pre- calibration of said module occurs during its insertion within the handle: the six cylindrical rollers 10 are arranged within their seat, and then a small elastic spring 11 is inserted in each one of the holes 24 until it is in contact with the respective rollers, and finally a small end ball 27 is inserted which is simply meant to keep and retain one end of the elastic spring perfectly aligned with the hole instead of allowing it to go into contact obliquely against the internal surface of the handle. After this, the internal bush 9 is inserted at the center in the pre-calibrated individual module and a thin washer with a large central hole is interposed immediately coaxially in order to separate the individual modules thus prepared. The pre-calibrated modules 23 are inserted within the handle, making the outer grooves 26 coincide with the respective rotation-preventing elements 5 jointly connected to said handle. Finally, the closure plug 1.2 of the handle is locked, providing a handle which is perfectly rigid and ready to be used without the need for further calibrations by the operator.

Of course, the invention is not limited to the examples of embodiment described above,

starting from which it is possible to provide other embodiments and manufacturing methods, and the details of execution can in any case vary without thereby abandoning the scope of the invention as stated and claimed in the appended claims.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.