GB2130933A

GB2130933A - Workpiece clamps

Info

Publication number: GB2130933A
Application number: GB08330738A
Authority: GB
Inventors: Olli Kytola
Original assignee: O KYTOLE JA KUMPP KY; O KYTOLA JA KUMPP KOMMANDIITTIYHTIO
Current assignee: O KYTOLE JA KUMPP KY; O KYTOLA JA KUMPP KOMMANDIITTIYHTIO
Priority date: 1982-11-19
Filing date: 1983-11-17
Publication date: 1984-06-13
Also published as: SE8306013L; GB2130933B; SE8306013D0; SE457422B; DE3340765C2; JPS59102576A; FI76012C; DE3340765A1; FI76012B; FI823990A0; FI823990L; GB8330738D0; JPH028868B2

Abstract

A workpiece clamp comprises a wedge member 3 drawn towards a base member 8 by means e.g. screw bolt 7, and co-acting with a wedge surface of a jaw 2 to move the jaw into a clamping position. As shown, two axially aligned wedge members 3, 4 act against a spring bias to move a pair of jaws 2, 3 into clamping engagement with a workpiece. A large clearance hole for the screwbolt allows the jaws to adapt to a limited extent to workpiece dimensions. <IMAGE>

Description

SPECIFICATION Fastening clamp The present invention is concerned with a fastening clamp in particular for the clamping of pieces to be machined, the said clamp comprising a wedge piece cut off at its tip or two wedge pieces cut off at their tips and placed symmetrically with their tips facing each other as well as a clamping jaw fitted against the slanting side of the wedge piece or pieces, the inclination of the edge or edges of the said clamping jaw equalling the inclination of the side of the said wedge piece or pieces, whereat the wedge piece or pieces is/are provided with a hole/holes for the tightening member and are displaceable by means of the tightening member in a direction perpendicular to their ends so as to fasten the piece to be machined between the clamping jaw and the counter-face.

The fastening clamps used in machine tools can be divided roughly into four different groups, of whose drawbacks the following should be stated: - The clamps for one piece only require a lot of time on replacement. Their space requirement is also high.

- Drawbacks of multiple fastening by means of an edge clamp are dimensional divergencies resulting from a multiplication of errors as well as the rising of the pieces apart from their fastening plane.

- Fixing irons etc. to be fastened from the top are hardly ever suitable for fastening of groups, because they cause the risk of collision for tools, and even the end milling of the top face is not possible when they are used.

- In the case of group clamps for pieces, the practice is highly varying. The operators design and make the necessary installation groups by themselves, or they have somebody else make these groups, because the tool dealers do not have a solution available for group clamping.

Along with the development of machine tools, the requirements imposed on the clamping of the pieces to be machined have also increased; from the "jig age" comprising one step, we have moved into NC or numerically controlled machining. This situation is seen most clearly, e.g., in the case of numerical machining centres, wherein a maximum number of pieces to be machined must be accommodated within the effective machining area of the machine tool. In such a case, excessively frequent exchanges of tools should be avoided, for such exchanges increase the requirement of servicing of the machine and slow down the performance of the work. Even during one working cycle, dozens of different tools have been programmed to perform various operations of face-levelling milling, recess-cutting, boring, threading, etc.

The fastening clamp in accordance with the present invention is mainly characterized in that the wedge piece is provided with at least two slanting sides against which at least two clamping jaws are fitted so as to fasten two or more pieces to be machined at different sides of the wedge piece.

When a fastening clamp in accordance with the present invention is used, by means of the same clamp clamping forces are generated both towards the clamping base and towards the surrounding guide frames.

The multi-directional fastening clamp in accordance with the invention shortens the time of exchange of the pieces, because an entire group is attached and detached by means of one movement.

The conical portions of the components of the fastening clamps have significance for the desired tightening force and above all for the ability to resist high machining forces. The multi-purpose fastener is suitable for most group ciampings. By means of its expanding, the clamp adapts the pieces against the guide frame and, at the same time, prevents the generation of any looseness relative the installation base.

Owing to lateral gliding of the jaws and to the large size of the central hole in the clamp, the fastening permits dimensional divergencies in the pieces. The precision of fastening is derived from the precision of the guide frame. The most reliable result is obtained when the finishing machining of the guide frame is performed in the same machine.

The fastening hidden between the pieces permit an unhindered machining within the entire area by means of face cutters etc., without risk of collision. It is to be noticed that, e.g., in NC machines, even little movements of evading may cause even hundreds of extra program statements in one cycle of working.

One of the best aspects of the fastening clamp, which is reliable in operation and favourable owing to its simple construction, is its versatile applicability. If required, the fastening plane can be raised by placing a raising piece between the installation base and the fastening clamp. The installation of the fastening clamp onto the base requires only one hole with inside threading in the base. Owing to the rapid exchange, the same clamp can be used at several different bases.

Owing to the small size and high efficiency of the fastening clamp, it requires only little space on the installation base.

The invention and its various applications will be described in more detail below with reference to the attached drawings, wherein Figure 1 shows one embodiment of a fastening clamp in accordance with the invention as a side view and in the initial position, Figure 2 shows the same clamp as a top view, Figure 3 shows the same clamp as a side view in the tightened position, Figure 4 shows the same situation as a top view, Figure 5 is a side view of a fastening clamp in accordance with the invention in its place of use before tightening, Figure 6 is a top view of different modes of using a fastening clamp in accordance with the invention, Figure 7 is a top view of a mode of using a fastening clamp in accordance with the invention, Figure 8 is a side view of the arrangement shown in Figure 7, Figure 9 is a top view of another mode of using a fastening clamp in accordance with the invention, Figure 10 is a side view of the arrangement shown in Figure 9, Figure 11 is a section view of a second embodiment of the fastening clamp in accordance with the invention, and Figure 12 is an exploded view of the wedge pieces and clamping jaws of a fastening clamp in accordance with a third embodiment.

Figure 1 2a is a side view of a fourth embodiment of the present invention, Figure 1 2b is a side view of a fifth embodiment of the present invention, Figure 1 2c is a top view of either one of the two embodiments shown in Figures 1 2a and 1 2b.

Figure 1 to 5 show an embodiment of a fastening clamp in accordance with the invention.

The fastening clamp is provided with two pieces 3 and 4 having central holes 1 and being of a shape of truncated edged cone, fitted with the tips facing each other. Between the edges cones, at their sides, two clamping jaws 2 are placed, whose inner faces are inclined so that the inclination corresponds to the slanting faces of the edged cones and whose ridges projecting towards each other assume positions in the space between the edge cones. The clamping jaws 2 are interconnected by means of a spring 5 passing through holes provided in the said jaws, which spring 5 attempts to pull the clamping jaws towards each other.

When a fastening clamp in accordance with the invention is being used, it is fitted, e.g. in the way shown in Fig. 5, between two pieces 10 to be secured to the base 8. The base is provided with a hole 13, whose threading corresponds to the threading of the bolt 7. The diameter of the bolt 7 is somewhat smaller than the diameter of the holes 1 in the edges cones 3 and 4. The bolt 7 is passed through the holes 1 in the edged cones 3 and 4. When the bolt 7 is being tightened by turning, it presses the upper edged cone 3 downwards, whereat the clamping jaws 2 move outwards apart from each other. Thereat the clamping jaws press the pieces 10 both against the base 8 and against the frame 9 surrounding the base. In Fig. 3, the effective forces are denoted with arrows A.

Fig. 6 shows the fastening-group base of a NCmachining centre. For the sake of illustration, different sorts of fastening groups have been drawn onto the same group base 8. The drawing shows the locations of the fastening clamps between the pieces 10 as well as the guide frame 9 surrounding the pieces 10. For the sake of clarity of illustration, different types of pieces are shown in groups: - three-way clamps for pieces of different forms, - four-way clamps for circular or angular pieces, - two-way clamps for pieces of different shapes, e.g. oblong, plank-shaped pieces.

In a four-way clamp, the edged cone 3 and 4 has four chamfered sides, against which four clamping jaws 2 are fitted in pairs opposite each other. The clamps hidden between the pieces permit a face cutting across the entire face plane as well as eliminate any risk of collision of the tools without any additional programming in NCboring.

The embodiment shown in Fig. 6 is also a practical example of different fastening-group bases. The fastening clamps have been in experimental use on those bases, and the results have been excellent. The fastening precision has been exactly in agreement with the guide frame.

The fastening clamps are closed and opened with a very light movement.

Figures 7 and 8 show an application in which so-called bundle clamping has been used. It can be carried out by placing the fastening clamps 12 in the middle of bundles of oblong pieces 10 to be clamped, whereat the dimensional deviations and the rising are considerably lower than, e.g., when an edge clamp is used.

Figures 9 and 10 show an embodiment in which a group clamping of longer pieces 10 has been achieved by means of two fastening clamps 12, an intermediate tube 1 and an extended screw 7. When the screw is threaded, both clamps operate at the same time and press the pieces 10 towards the base 8 and the frame 9.

Fig. 11 shows an alternative embodiment of the fastening clamp. Instead of a clamping jaw provided with two chamfered sides, so-called semi-jaws 6 are used which, together with the edged cone 3, form a so-called low-clamp. By the effect of the edged cone, the jaws move without play against the installation base 8.

Above, the invention has been described so that the base is placed horizontally underneath the pieces to be clamped. Of course, the invention can be applied equally well also to fastening of pieces, e.g., onto a vertical base, in which case the edged cone 3 is not placed above the other edged cone 4, but they are fitted side by side, the axes of the holes being positioned horizontally.

Besides onto a base provided with a threaded hole, the clamp can also be installed onto the Tgroove of the machine by means of a bolt and a nut. A hydraulic cylinder can also be used as the tightening member.

The slanting sides of the wedge piece 3 may also be slightly convex, in which case the clamping jaw may turn to some extent and become placed better against the piece to be machined.

Fig. 12 shows an application in which the inner sides of the clamping jaws 2 are provided with Vgrooves, whereat both jaws are guided by two slanting sides of the wedge piece 3.

Referring to Figures 1 2a and 1 2c, the fastening clamp shown has two similar clamping jaws 2a and two wedge pieces 3a and 4a. The clamping jaws 2a are shaped slightly differently from the clamping jaws 2 shown in Figure 12 in that they have opposed flat abutment surfaces 1 3. As can be seen in Figure 1 2c the clamping jaws 2a are provided with V-shaped grooves which cooperate with the V-shaped configuration of the sides of the wedge pieces 3a, 4a.

There are four screw members 14, one on the two opposed sides of each of the jaws 2a. The head of each screw member 14 protrudes from the jaw 2a. A spring 5a in the form of a closed loop is fitted over the heads of neighbouring screw members 14 so that there are two spring loops 5a biassing the jaws 2a together.

The fastening clamp of Figures 1 2a and 1 2c operates in a similar way to that shown in Figures 2-5. When a bolt 1 a which extends through the wedge members 3a, 4a into a base (not shown) is screwed into the base. This causes the upper wedge piece 3a to move downwardly thereby moving the jaws 2a downwardly and outwardly to clamp a work piece.

The fastening clamp of Figure 1 2b has only a single wedge piece 3b which is a complementary fit between two flat-bottomed jaws 2b. The embodiment of Figure 1 2b is identical in top view to that of Figure 1 2a with the same arrangement of screw members 1 4 and springs 5a. The embodiment of Figure 1 2b works in a similar way to the embodiment shown in Figure 11 in that, when the screw 1 b is screwed into a base (not shown), this causes the wedge piece 3b to move downwardly thereby parting the jaws 2b against the force of the springs 5a.

Claims

1. Fastening clamp in particular for the clamping of pieces (10) to be machined, the said clamp comprising a wedge piece (3) cut off at its tip or two wedge pieces (3, 4) cut off at their tips and placed symmetrically with their tips facing each other as well as a clamping jaw (2, 6) fitted against the slanting side of the wedge piece or pieces, the inclination of the edge or edges of the said clamping jaw equalling the inclination of the side of the said wedge piece or pieces, whereat the wedge piece or pieces is/are provided with a hole/holes (1) for the tightening member (7) and are displaceable by means of the tightening member in a direction perpendicular to their ends so as to fasten the piece to be machined between the clamping jaw and the counter-face (9), characterized in that the wedge piece (3, 4) is provided with at least two slanting sides against which at least two clamping jaws (2, 6) are fitted so as to fasten two or more pieces to be machined at different sides of the wedge piece.

2. Fastening clamp as claimed in claim 1, which is provided with two wedge pieces (3, 4), characterized in that both of the said wedge pieces (3, 4) can be pressed by means of the tightening member (7) towards the installation base (8).

3. Fastening clamp as claimed in claim 1 or 2, characterized in that the diameter of the hole (1) in the wedge piece (3, 4) is larger than the diameter of the fastening member (7).

4. Fastening clamp as claimed in any of claims 1 to 3, characterized in that it is provided with a spring (5) for returning the clamping jaws (2).

5. Fastening clamp as claimed in any of claims 1 to 4, characterized in that the wedge piece (3, 4) rests axially against the installation base (8) either directly or by the intermediate of a piece.

6. Fastening clamp as claimed in any of claims 1 to 5, characterized in that the tightening member is a threaded screw (7) or a spindle displaced by means of a pressure cylinder, an eccentric cam or equivalent.

7. Fastening clamp as claimed in any of claims 1 to 6, which is provided with two wedge pieces (3, 4), characterized in that the clamping jaws (2) are provided with two slanting faces, whose inclination corresponds to the slanting faces of the wedge pieces (3, 4) and in which clamping jaws (2) the edge between the slanting faces becomes positioned in the space between the wedge pieces (3, 4).

8. Fastening clamp as claimed in claim 1, 3, 5, or 6, which is provided with one wedge piece (3), characterized in that the clamping jaws (6) are provided with one slanting face, whose inclination corresponds to the slanting faces of the wedge piece (3).

9. Fastening clamp as claimed in claim 8, characterized in that the wedge piece (3) can be pressed by means of the tightening member (7) towards the installation base (8).

10. Fastening clamp as claimed in any of claims 1 to 9, characterized in that the slanting inside faces of the clamping jaws (2, 6) are provided with guide grooves or V-groove bottoms, each jaw being guided by two faces of the wedge piece (3, 4).

11. Fastening clamp as claimed in any of claims 1 to 9, characterized in that the slanting faces of the wedge pieces (3, 4) are convex as viewed in the direction of gliding.

12. A clamping device suitable for use with workpieces to be machined comprising at least one wedge-shaped member disposed adjacent a clamping jaw and means for moving the wedgeshaped member in a first direction relative to the clamping jaw, wherein the wedge-shaped member has a sloping face which co-operates with a complementary face on the clamping jaw so that the movement of the wedge-shaped member causes movement of the clamping jaw in a second direction angularly dispiaced from the first.

1 3. A fastening clamp substantially as herein described with reference to Figures 1-10, Figure 11, Figure 12 or Figures 1 2a and 1 2c or Figures 12band 12c.