WRENCH FOR INSERT HOLDERS OF THE BLADE TYPE

Abstract: The invention relates to a key for insert holders of the kind that includes a blade shaped body (4) having a slot (5) intended to receive an insert, said slot (5) being defined by an elastically flexible clamping arm (7) for clamping the insert. The key has a shaft (1) with two projections for engaging laterally opening seats in the body (4) and the clamping arm (7) respectively. One of these two projections is provided on a pivoting link (12) that is connected with the shaft via a hinge (13). The sum of the partial distances between the hinge (13) and the two projections is larger than the distance between the seats of the insert holder when the clamping arm is stressfree. Pivoting of the shaft beyond an unstable position of equilibrium thus makes the clamping arm (7) to deflect by a predetermined value.

Description: WRENCH FOR INSERT HOLDERS OF THE BLADE TYPE Technical Field of the Invention The present invention relates to a key for insert hold- ers of the kind that include a blade or disc shaped body having a slot intended to receive an insert, said slot being defined by an elastically flexible clamping arm provided to resiliently clamp the insert in the slot, said key comprising a shaft having two projections for engaging laterally opening seats in the body and the clamping arm respectively, more precisely in order to deflect the clamping arm so as to widen the slot in connection with the mounting and/or dismounting of an insert . Prior Art A clamping key of the kind generally defined above is previously known from EP 0 654 316 (see figures 6-8) . In this case the two projections are fixed upon the shaft, more precisely quite close to each other in the area of one end of the shaft. The fact that the projections are fixed upon the key shaft means, on one hand, that the user always has to apply a force upon the shaft in order to maintain the clamping arm deflected and the slot widened and, on the other hand, that the deflection of the clamping arm will be effected in a way that is hard to control since the deflection is determined only by a discretionary judgement of the user. Thus, if the user applies an excessive force upon the shaft there is a risk that the clamping arm is subjected to a permanent, plastic deformation that in practice means that the insert holder in its entirety has to be rejected. The circumstance that the user has to permanently apply a manual force upon the shaft in order to maintain the slot widened (or reversed that the flexible clamping arm returns to a clamping position as soon as the user lets the shaft free) has the further consequence that exchange of insert may be complicated to an unnecessary high degree, especially when the tool is located in such a way that it is difficult to reach. Thus, the key shaft has to be manually - and by a considerable force - kept in an active, slot widening position not only during the sequence when a worn insert is to be removed from the slot, but also during a later sequence when a new insert should be positioned therein. It should also be mentioned that the short distance between the projections of the known key means that the required lever action between the projections becomes mediocre and the user has to use a comparatively large manual force in order to deflect the clamping arm outwards. Objects and Features of the Invention The present invention aims at removing the shortcomings mentioned above in connection with the previously known clamping key and at creating an improved key. Thus, a primary object of the invention is to create a key that automatically, i.e. without depending upon the activities of the user, maxi- mises the deflection of the clamping arm in order to permanently keep the deflection within the elastic area. In other words the clamping arm must not by accident be deflected so far that a plastic deformation occurs. A further object is to create a key that is automatically maintained in the active position where the clamping arm is kept deflected and the slot widened in order to eliminate any need of the user to physically hold and apply a force upon the key shaft in connection with the actual exchange of insert. Still an object of the invention is to create a key that is structurally simple and cheap to manufacture and makes it possible to deflect the clamping arm by using a moderate physical force. According to the invention at least the primary object is attained by means of the features defined in the characterizing part of claim 1. Preferred embodiments of the invention are furthermore defined in the dependent claims. Brief Description of the Drawings In the drawings: Figure 1 is a perspective view of a clamping key according to the invention, Figure 2 is a side view seen along an edge surface of the same key, Figure 3 is a perspective view showing the key in connection with an insert holder, more precisely in an initial position before the deflection of an adherent clamping arm, Figure 4 is a partial side view showing an insert holder and an insert applied in said insert holder as well as a key according to the invention, Figure 5 is a side view corresponding to figure 4, though without any insert, Figure 6 is a perspective view showing the insert holder as well as the key in an active position when the clamp- ing arm is deflected outwards, and Figure 7 is a side view showing the key as well as the insert holder in the same position as in figure 6. Detailed Description of a Preferred Embodiment of the Inven- tion The key shown in figure 1 and 2 includes an oblong shaft 1 and two projections 2, 3 that project laterally from said shaft. Before the key is described more in detail reference is made to figures 4 and 5 that illustrate an insert holder that in a known way is in the shape of a blade-shaped or discshaped shaped body 4 that is provided with a slot 5 that forms a seat for an insert 6. The slot is defined by a comparatively narrow clamping arm 7 that is elastically flexible relative to the body 4, said arm 7, due to its inherent elasticity, being able to clamp the insert in the desired position. Seats 8, 9 are recessed in the clamping arm 7 as well as in the body 4, said seats 8, 9 being adapted to receive the two projections 2, 3 of the key. These seats may either consist of through- going holes or of recesses that open only at one side of the insert holder. So far described the tool, composed of the insert holder and the insert, and the key are in all essentials previously known . Reference is again made to figures 1 and 2 from which it is evident that the key shaft 1 has the shape of an oblong rod being rectangular in cross section. The rod presents two opposite, relatively wide longitudinal side surfaces 10 and two narrower edge surfaces 11. The dimensions of the shaft may vary depending on the dimensions of the insert and the insert holder. However, the length of the shaft should be within the range of 100 to 200 mm, while the width is 8 to 15 mm and the thickness 2 to 4 mm. According to the invention the projection 2 is provided on a link 12 that is connected with the body 4 of the insert holder via a hinge or articulation 13. Consequently said link may pivot relative to the shaft. More precisely, the hinge 13 is located in the area of one end of the link while the projection 2 is located in the area of the opposite end. As is evident from the drawing the projection 2 has the shape of a cylindrical pin. On the side of the flat link 12 that is opposite the pin 2 there is a third projection 14, also in the shape of a cylindrical pin. Said third pin 14 forms a stop element that restricts the possibilities of the link to pivot relative to the shaft. In the shown, preferred embodiment the pin 14 co-operates with an arc-shaped recess 15 in the shaft. More precisely this recess opens in one of the two narrow edge surfaces 11. The other projection 3, that likewise is in the shape of a cylindrical pin, is fixed upon the shaft, more precisely at a point located closer to one end of the shaft than the hinge 13. The diameter of the pin 3 (as well as the pin 2) is only slightly less than the diameter of the seat 9 (and the seat 8 respectively) recessed in the insert holder in order to have the pin inserted into the seat with a relatively close fit. Between the pin 3 and the shaft 1 there is a thickened material portion 3' having an annular shoulder surface 16. The axial extension of the material portion 3' is essentially equal to the thickness of the link 12. This guarantees that the shaft 1 is oriented essentially parallel to the disc shaped holder 4 when the two pins 2, 3 are inserted into its adherent holes 8, 9. Characteristic of the invention is that the sum of on one hand the centre distance between the hinge 13 and the pin 3 and on the other hand the centre distance between the hinge 13 and the pin 2 is at least somewhat larger than the centre distance between the two holes 8 and 9 when the clamping arm is unaffected, i.e. stressfree. As is evident from figures 1-3 the pin 3 on one side of the shaft 1 has its counterpart also on the opposite side of the shaft, i.e. in the shape of a cylindrical pin 3A. In an analogous way there is a cylindrical pin 2A on the opposite side of the link 12, said pin corresponding to the pin 2. The pin 2A constitutes a prolongation of the stop pin 14, more precisely in the shape of a material portion having a smaller diameter than the material portion that forms the stop pin 14. By the presence of the cylindrical pins 2A and 3A the key may free of choice be oriented with either one of its two opposite sides facing the insert holder. The Function and the Advantages of the Invention When the insert 6 is to be removed the key is initially applied in an initial position (see figures 3 and 4) in which the pins 2, 3 engage the seats 8, 9, and in which the link 12 is pivoted a distance away from the shaft. From this initial position the shaft is pivoted manually in a direction towards the stop pin 14, said pin 3 serving as a hinge point for the pivoting motion. In a given pivoting position, where the stop pin 14 is still distanced from the recess 15, the geometrical centre of the hinge 13 will cross an imaginary straight line between the centres of the seats 8, 9. In this state, constituting an unstable position of equilibrium, the centre dis- tance between the pins 2 and 3 is larger than the distance between the seats 8, 9 in a stressfree state of the clamping arm 7, since the sum of the partial distances between the pin 2 and the hinge 13 respectively the hinge 13 and pin 3 is larger than the distance between the seats 8, 9. This means that the elastic clamping arm 7 in this position is deflected while widening the slot 5. From the unstable position of equilibrium the shaft may be pivoted further a short distance until the stop pin 14 completely engages the recess 15, i.e. contacts its bottom. In this end position the centre distance between the pins 2 and 3 has decreased somewhat in comparison with the corresponding distance in the unstable position of equilibrium. Nevertheless said centre distance in said end position is still so large that the clamping arm is maintained in a deflected state in order to allow the insert 6 to be freely removed out of the slot without actuation from the clamping arm. While the key is still applied in the end position mentioned above a new insert (or the same insert indexed 180°) may be inserted in the widened slot. Not until an insert is again in position in the slot the shaft of the key need to be pivoted back to its initial position, the clamping arm again firmly clamps the insert while the shaft during its return movement passes the unstable position of equilibrium where the slot is widened to a maximum degree. The described clamping key has several advantages. An important advantage is that the deflection of the clamping arm is compulsory maximised to a value where a plastic deformation cannot appear. Thus the clamping arm may never be deflected further than what is defined by the maximum distance between the pins 2, 3 when the hinge 13 passes the unstable position of equilibrium. In other words the user may not by accident - by using an uncontrolled large force - deform the clamping arm in such a way that it becomes useless. Another advantage is that the key may automatically be maintained on the insert holder in connection with the exchange of insert, i.e. without any need for the user to hold it. By the geometry of the key it is thus guaranteed that the hinge 13 - from the unstable position of equilibrium - may pass a short distance beyond the straight line between the seats 8, 9 and safely be maintained in an irreversible way in its inner end position, since the clamping arm 7, due to its inherent elasticity, permanently strives to keep the shaft pivoted towards its inner end position. The fact that the key is automatically maintained in its inner end position, while the slot is continuously widened, allows the operator to dismount and re-mount respectively an insert at different times without having to handle the key. A further advantage of the clamping key according to the invention is that the transmission ratio between the comparatively long shaft and the relatively short lever arm that is constituted by the distance between the hinge 13 and the pin 2, is comparatively large, this guaranteeing that also rigid clamping arms will be deflected by using a reasonable manual force. Feasible Modifications of the Invention The invention is not solely restricted to the embodiment described and shown in the drawings. Thus it is feasible to provide not only a first one, but also the other one of the two projections on a pivoting link, said projections being intended to be applied to the seats of the insert holder. In such cases each projection is applied to a link that is connected with the shaft by an individual hinge, said projections being connected with each other by a third link. Thus, the only essential thing according to the invention is that at least one of the projections is provided on a pivoting link so as to vary the distance between the projections by pivoting the shaft, more precisely from an initial position in which said distance corresponds to the distance between the seats of the insert holder and the clamping arm is stressfree, to a maximum value where the distance between the projections is, on one hand, sufficiently large to provide a widening of the slot, but, on the other hand, not so large that the clamping arm will run the risk of being plastically deformed. It should also be mentioned that the key may include two links, for instance links whose distance to the hinge are different in order to be able to use the key in connection with different insert holders.

Claims: Claims 1. Key for insert holders of the kind that include a blade or disc shaped body (4) having a slot (5) intended to receive an insert (6), said slot (5) being defined by an elastically flexible clamping arm (7) provided to resiliently clamp the insert in the slot, said key comprising a shaft (1) having two projections (2, 3) for engaging laterally opening seats (8, 9) in the body (4) and the clamping arm (7) respectively, more precisely in order to deflect the clamping arm, so as to widen the slot, in connection with the mounting and/or dismounting of an insert, c h a r a c t e r i z e d in that at least a first one (2) of said two projections (2, 3) is provided on a pivotable link (12) connected to the shaft via a hinge (13), and that the sum of the distances between, on one hand, the hinge (13) and the first projection (2), and on the other hand, the hinge (13) and the other projection (3) is larger than the distance between said two seats (8, 9) when the clamping arm (7) is stressfree. 2. Key according to claim 1, c h a r a c t e r i z e d in that the second projection (3) is fixed upon the shaft (1), more precisely at a point located closer to an end of the shaft than said hinge (13). 3. Key according to claim 1 or 2, c h a r a c t e r i z e d in that a third projection (14) is provided at one side of the link (12) that is opposite said first projection (2), said third projection (14) constituting a stop element intended to restrict the pivoting motion of the link, more precisely to an active end position in which the third projection abuts the shaft when the distance between the first and second projections (2, 3) is at least somewhat larger than the distance between said seats in a stressfree state of the clamping arm. 4. Key according to any one of the preceding claims, c h a r a c t e r i z e d in that at least the first and second projections (2, 3) are in the shape of cylindrical pins. 5. Key according to claim 4, c h a r a c t e r i z e d in that between the fixed pin (3), forming a projection, and the shaft (1) there is a thickened portion (3') having a length that corresponds to the thickness of the link (12) . 6. Key according to any one of the preceding claims, c h a r a c t e r i z e d in that the shaft is in the shape of an oblong rod (1) having a rectangular cross section, said rod (1) having two opposite wide side surfaces (10) and two opposite, narrower edge surfaces (11) . 7. Key according to claim 6, c h a r a c t e r i z e d in that the hinge (13) is located in the area of a narrow edge surface (11) in order to be located at a certain distance from an imaginary straight line between the first and second projections (2, 3), when the link (12) is pivoted to its active end position, said link being irreversibly maintained in this position as long as the shaft is not actuated.

Inventors: HANSSON PER, HANSSON, PER
Applicants: HANSSON PER, SANDVIK AB, HANSSON, PER
Application year: 1998
Main classification: B23B27
IPC codes: B23B27, B25B33