US2772708A - Integral loop blade-anchoring means for high-frequency reciprocating saws - Google Patents

Description

Dec. 4, 1956 F. M. MIQUEL 2,772,703

INTEGRAL LOOP BLADE-ANCHORING MEANS FOR HIGH-FREQUENCY RECIPROCATING SAWS Filed Nov. 28, 1955 United States Patent INTEGRAL LOOP BLADE-ANCHORING MEANS Eggs HIGH-FREQUENCY RECIPROCATING Francois M. Miquel, Paris, France, assignor to Socit Anonyme Tubest, Paris, France, a French company Application November 28, 1955, Serial No. 549,530

Claims priority, application France December 3, 1954 3 Claims. (Cl. 143133) This invention relates to saws and, more particularly, to saws of the type in which the blade is mounted taut between the elastic ends of the two arms of a U-shaped support which carries e. g. electro-magnets to set one of said ends itno high frequency vibrations which are transmitted to the blade to cause penetration of the same into the part to be sawn.

Heretofore, in known saws of this type or electrosaws, the blade was mounted between the two' support arms by means of holding pins passing through the ends of the blade, the ends of the support arms each being provided with three difierent pairs of fingers (each pair corresponding to a given orientation of the cutting edge of the blade with respect to the U-shaped support plane) which are slightly spaced apart so as to leave therebetween the narrow slot provided between each pair of fingers accommodating the blade of which the holding pin is disposed behind the finger pair, so as to be mounted taut owing to the elasticity of the ends of the support arms.

It has been found, in practice, that this kind of mounting is not quite satisfactory.

As a matter of fact, this kind of mounting gives rise to an objectionable phenomenon capable, on the one hand, of impairing the working efliciency and, on the other hand, of causing a rapid destruction of the blade.

The said phenomenon consists in shocks occurring between the pins carried on the ends of the blade and the fingers behind which said pins are engaged, said shocks recurring at a high rate due to the high frequency of the vibrations generated by the relative displacements between the blade and the support arms. Under 'the action of said shocks, the holding pins subject the blade to shearing stresses, while more or less rapidly widening their mounting holes. With time, one end of the blade is finally released and violently projected away under the action of the vibrations.

Moreover, the mounting hole has the drawback of weakening the blade which is thus more breakable.

This invention has for its puropse to obviate these drawbacks and, more particularly, to provide, between the elastic support and the blade, a connection capable of eliminating the above mentioned phenomenon.

An object of the invention is to bend each end of the blade into a loop made in such a manner that the blade may be engaged in the usual fashion between the fingers provided on the ends of the support arms, said loops bearing behind said fingers to hold the blade assembly.

This arrangement offers several essential advantages.

There is thus substituted for the conventional rigid abutment member (holding pin) an elastic member constituted by the above mentioned loop which is an efficient means for absorbing the shocks resulting from the vibrations.

Moreover, said shocks are particularly eliminated since elastic deformations of the loops follow the to-and-fro displacements of the vibrating ends of the support arms.

Furthermore, the blade according to the invention constitutes a one-piece member (instead of being constituted by three separated, interconnected elements, viz. a blade and two holding pins) which avoids, ipso facto, any risks of dismantling of the assembly. Finally, the blade is no more provided with any hole, which makes it far stronger.

Another object of the invention is to provide a saw of the type described, wherein the above mentioned loop offers the shape of a right cylinder and comprises a fiat extension extending in a plane parallel with the main blade portion, said flat extension being engaged against said main portion between the two fingers of the relevant pair of fingers.

This further disposition offers the additional advantages that the two halves of the loop, located on either side of the blade plane, cooperate to absorb the shocks and to elastically hold the blade taut. Moreover, the two elements thus engaged between the fingers tend to be urged away from each other by the elasticity of the loop which considerably improves the resistance of the blade in a direction transverse to its plane while opposing relative displacement of the blade with respect to the vibrating arm ends.

Other objects and advantages of the invention will be apparent from the following detailed description, together with'the accompanying drawings, submitted for purposes of illustration only and not intended to define the scope of the invention, reference being had for that purpose to the subjoined claims.

Figure l is an elevational view of a vibrating sawblade of a conventional type mounted in its anchoring fingers,

Figure 1a illustrates, also in elevational view, a detail of Figure 1,

Figure 2 is a corresponding plan view,

Figure 3 is a cross-sectional view along line 33 of Figure 1,

Figure 4 is a view similar to that of Figure 3, under other conditions,

Figure 5 is an elevational view of a vibrating saw-blade according to the invention,

Figure 6 is a longitudinal sectional view along line 6-6 of Figure 5,

Figure 7 is a sectional view along line 7-7 of Figure 5, and

Figure 8 is a perspective view of a vibrating saw, the blade of which is designed according to the invention.

Referring first to Figure l, 1 is a vibrating saw-blade of a conventional known type with two pins 2, 3 extending through suitable holes of the blade. Each pin' bears against the outer faces of one of two anchoring fingers 4, 5 arranged pairwise at the ends of extendsions of two branches of a U-shaped support such as the support 6 represented in Figure 8. The extension of one of the branches of the support 6 is constituted by a flexible branch 11 which carries both fingers 4, whereas aligned with the other branch of the support 6 is a small plate 12 secured, by a leaf spring 13, to two bent lugs 14 riveted on the corresponding branch of the U-shaped support. The small plate 12 constitutes the movable armature of an electromagnet 15 carried by the lugs 14 according to a well known arrangement, and it is formed into two fingers 5 for anchoring the saw-blade.

The assembly further comprises a handle 16, a current supply cord 17 and a trigger 18 for actuating a switch in the energizing circuit of the electro-magnet.

As a rule, the movable armature 12 has two further pairs of fingers 5a, 5b for anchoring the saw-blade in two other different planes. The end of the flexible branch 11, furthermore, has a slot 4a and a further pair of anchoring fingers 4b, the edges of the slot 4a and the fingers 4b being adapted for cooperating with the fingers a and 5b respectively for the purpose of holding and maintaining the saw-blade in two positions different from that represented in Figure 8.

When the saw is in operation, the movable armature 12 is vibrating and, as it is attracted, it carries with it the saw-blade 1 (Figure 1) through the medium of the lower pin 3, whereas the upper pin 2 pulls down the flexible branch 11. As the armature 12 is released, the flexible branch 11 pulls up the saw-blade back into rest position through the agency of the upper pin 2.

After completion of the active stroke of the armature 12, i. e. when the latter abuts against the stationary core of the clectro-magnet 15, the saw-blade 1 and the lower pin move on, under the effect of their inertia, a very short distance, it is true, and practically not likely to be perceived, but, however, of an amplitude sufficient for causing thepin 3 to be disengaged from the anchoring fingers 5 (see Figure 4). Immediately afterwards, the resiliency of the branch 11 brings the pin 3 back into Contact with the fingers 5. There occur, therefore, repeated impacts of the pin 3 against the fingers 5, at a high frequency which corresponds to the vibrating frequency of the electro-magnet. Such repeated impacts lead to pronounced hammering effect on the metal portions of smaller cross-sections, i. e. the pin and the wall of the hole through the blade into which it is threaded. The hole soon becomes elongated (Figure la) and the pin frequently snaps out of the blade or the blade breaks at the level of the hole under the action of the repeated impacts of the pin against the edge of the enlarged hole of the blade.

In order to obviate these drawbacks, according to the invention, the saw-blade, instead of being provided with a hole at each end, is bent into a loop 21, as shown in Figures 5 and 6, said loop being adapted to abut against the anchoring fingers 4 and 5. Preferably, each end of the loop is bent flat against the blade itself along a certain length, as shown at '20 in Figure 6, so that it may be also introduced between the two fingers of the relevant pair.

The saw-blade 22, according to the invention is clearly shown in Figure 8, in mounted position, on the conventional support described above.

It is obvious that this new saw offers several advantages. First of all, the blade proper with its saw-tooth cutting edge and its anchoring loops is in one piece, so that the said anchoring loops integral with the blade do not risk being separated therefrom. Furthermore, the loop shaped anchoring members offer a certain degree of elasticity owing to which they always remain pressed against the v 4!. anchoring fingers. As a result, no shocks ever occur'between said loops and fingers. The work effected with such a saw is extremely uniform without any hammering effect on the contacting surfaces; the blade is not weakened by any hole. Now, with a conventional blade such as shown in Figures 1 and 2, if the thickness of the blade is smaller than the width of the gap between the anchoring fingers 4, the blade is likely, during a workout, to be shifted into planes no more coinciding with the general plane of the support, as shown in dot-dash-line in Figure 2. Such deviations areobviously liable tojeopardize the accuracy and smoothness of the work effected. As a contrast with the saw-blade 22, according to the invention, the root of the loop is jammed between the anchoring fingers, so that any clearance between said blade and fingers is avoided even if the spacing between the latter is greater than the thickness of the blade.

While the invention has been described with particular reference to a preferred embodiment, it is not intended to limit the scope of the invention to the embodiment illustrated, nor otherwise than the terms of the subjoined claims.

What is claimed is:

l..A saw-blade of the type having both its ends provided with anchoring means to hold said blade taut upon its engagement into aligned anchoring slots, provided in the ends of the arms of the support of a vibrating saw of the type described, said blade being characterized by the feature that the anchoring means of at least one of its ends are constituted-by said end itself bent into a loop adapted to bear under elastic deformation against the outer edges of one of said slots upon engagement of said blade into both of said slots, whereby said loop permanently remains in contact with said edges upon vibrationof said armsunder alternate re-assuming of its non strained initial shape and further increase of said elastic deformation.

2. A saw-blade to be removably mounted in a vibrating saw of the type described including alignedtanchoring slots, said blade having both its ends each bent into a loop.

3. A saw-blade according to claim 1, wherein said loop has the shape of a right cylinder and is provided with a flat extension in generally parallel relationship and closely spaced from the unbent portion of the blade, so as to be engageable together therewith into said anchoring slot.

References Cited in the file of this patent UNITED STATES PATENTS 1,227,902 Frost May 29, 1917 1,708,278 ,Mendel Apr. 9 1929 2,233,862 Dremel Mar. 4, 1941

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