GB2262904A - Shaver cutter drive - Google Patents

Abstract

A dry shaver has first and second linear cutters mounted for counter-reciprocatory motion relative to the shaver body, drive means for driving the cutters; and a linkage for coupling the cutters to the drive means. The linkage comprises first and second pairs of opposed limbs (10, 11; 12, 13) forming a parallelogram arrangement. Each limb (10, 11) of the first pair is mounted on the shaver body, whilst each limb (12, 13) of the second pair provides a drive input to a respective cutter. The drive means causes oscillatory motion of the parallelogram linkage. <IMAGE>

Description

Shaver Cutter Drive This invention relates to a dry shaver having first and second linear cutters mounted for reciprocatory motion relative to the shaver and means mounted to the shaver to drive the cutters.

Electric dry shavers are well known, which have an arched shaving foil and an inner cutter pressed against the inside of the arch and driven in reciprocatory motion in the lengthwise direction of the arch, for cutting hairs which extend through a multitude of small apertures in the foil. Even with a single foil, noise and vibration cause problems.

In recent years there has been a tendency to move to shavers which have two parallel arched foils each with its own inner cutter, and with both of the foils having some capacity for movement relative to the shaver body. In this way, a closer shave is more likely to be obtained, but noise and vibration problems are exacerbated.

With shavers having two floating foils, the provision of effective drive means to the separate inner cutters presents problems. In use of dry shavers, it is inevitable that shaving debris is present below the shaving foils. Conventionally, the foils are provided in a shaving head, which is removable for cleaning away shaving debris which has accumulated beneath the foils. The foils are attached to the removable head, whereas the inner cutters are attached to the shaver body, and so are exposed, upon removal of the head, for cleaning around the inner cutters.

For shaving efficiency, of course, the inner cutters must be free to move to follow all the movements of the shaving foils. Providing a drive to such "fully floating" inner cutters involves relative movement between a succession of drive elements. Such complex drive systems introduce unwanted inertia into the drive system, add to the cost of the shaver, and are always liable to increase the amount of noise and vibration occurring when the shaver is in use. It is an object of the present invention to simplify the cutter drive in such shavers.

In a separate patent application, filed on the same date as the present application, there are proposals to integrate the cutters within the removable shaver head. By mounting the cutters in the removable head, the floating mounting of the cutters can be separated from the drive to the cutters. This separation opens up possibilities for simpler drive systems to fully floating cutters. The present invention has particular application to the shavers of the companion patent application, in which the cutters are carried within the removable shaving head.

According to the present invention there is provided a dry shaver having first and second linear cutters mounted for counter-reciprocatory motion relative to the shaver body; drive means for driving the cutters; and a linkage for coupling the cutters to the drive means; characterized in that: said linkage comprises first and second pairs of opposed limbs forming a parallelogram arrangement; each limb of the first pair is mounted on the shaver body; each limb of the second pair provides a drive input to a respective cutter; and said drive means is arranged to cause oscillatory motion of the parallelogram linkage.

The drive means can be a pin, mounted eccentrically on a drive shaft extending from the body of the shaver, the eccentric pin engaged within a slot of a drive flange itself provided on one of the two limbs of the second pair of the parallelogram linkage. In this way, rotation of the drive shaft causes the eccentric drive pin to describe a circle, and this circular motion within the slot of the drive flange causes the limb of the parallelogram which carries the flange to reciprocate backwards and forwards through one cycle with each cycle of rotation of the drive pin.This reciprocatory motion of the driven limb is transmitted, through the first pair of limbs of the parallelogram linkage to the opposite side of the parallelogram, that is, the other of the two limbs of the second pair on the parallelogram and, in this way, the limbs of the second pair are put into counter-reciprocatory motion. By providing a drive peg on each of these two limbs of the second pair, with each one of these pegs engaging in a slot in a different one of the two cutters of the shaver, the counter-reciprocatory motion of the parallelogram is perpetuated in a corresponding counter-reciprocatory motion of the two cutters.

As the drive to the cutters is not required to impose on the cutters any spring force pushing the cutters into contact with the associated foils, and the cutters are mounted on the foils by means separate from the drive, it is sufficient for transmission of drive from the parallelogram to the cutters to have a simple transverse slot in each cutter to receive the upstanding drive peg from one of the two limbs of the second pair of the parallelogram. Naturally, any transverse motion of the cutters, induced by transverse motion of the foil as the foil moves over the skin of the user, is accommodated by relative motion of the drive peg in the slot of the cutter.

However, even if there is no foil-induced transverse motion of the cutter, there will still be some transverse movement of the drive peg in the cutter slot, simply because the distance separating the limbs of the second pair of the parallelogram linkage varies cyclically with the reciprocatory motion of the parallelogram.

For a better understanding of the present invention, and to show more clearly how the same will be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a plan view of a parallelogram linkage cutter drive for a shaver in accordance with the present invention Figure 2 schematically illustrates a perspective view of a modified parallelogram linkage cutter drive, employing living hinges, in a central position; Figure 3 shows the parallelogram linkage cutter drive of Fig. 2 in one extreme position; Figure 4 shows a further embodiment of parallelogram linkage to drive employing an offset drive arrangement, in one extreme position; Figure 5 shows the cutter drive of Fig. 4 in the other extreme position; and Figure 6 shows the cutter drive of Figs. 4 and 5 in the central position.

In all three illustrated embodiments, corresponding reference numerals are mostly employed for corresponding parts. Where a part is significantly modified, however, a modified reference numeral is also employed.

Referring to Fig. 1, a parallelogram has a first limb 10 and second limb 11 of a first pair of opposed parallelogram limbs, and a first limb 12 and second limb 13 of a second pair of opposed parallelogram limbs. A pivot pin 14 connects limbs 10 and 12, a pin 15 connects limbs 12 and 11, a pin 16 connects limbs 11 and 13 and a pin 17 connects limbs 13 and 10.

Halfway along the length of limb 10 is a bore by means of which the parallelogram linkage is mounted on the shaver body by a peg 18. A similar bore in the middle of limb 11 accommodates a similar peg 19 for mounting on the shaver body.

Beneath the parallelogram linkage is a drive shaft which carries an eccentric drive pin 20. This engages with a slot 21 in a flange 22 which extends out of the limb 13 into the space 23 in the middle of the parallelogram. The length direction of the slot 21 is transverse to the line joining the pegs 18 and 19.

The rotational axis of the drive shaft on which the drive pin 20 is mounted, and the pegs 18, 19, all lie in the same plane. Thus, it will be appreciated that rotation of the drive shaft, with consequent movement of the drive pin 20 around a circular locus, causes the flange 22 to reciprocate up and down as seen in the drawing. The chain dotted lines in the drawing show the position 24 of the flange 22 when the drive pin 20 is at the "6 otclock position of the drive pin 20, when seen in the drawings.

At mid-length, the limb 12 carries a drive peg 25 and at mid-length on the limb 13 there is a similar drive peg 26. It will be appreciated that the reciprocatory motion of the parallelogram linkage causes an identical reciprocatory motion of the drive pegs 25, 26. Each of these two drive pegs engages in a transverse slot of a different one of two linear reciprocatory cutters of the shaver (not shown).

The chain dotted lines in the drawing illustrate how the limbs 12 and 13 are closer together at opposite ends of the reciprocatory motion than they are (as shown in continuous line) at the mid-point of the reciprocatory motion. Thus, not only do the drive pegs 25 and 26 move up and down as seen in the drawing but they also have a relatively small component of motion in the transverse direction, from side to side, as seen in the drawing, during each cycle of reciprocation.

The embodiment of Fig. 1 relies on pivot pins at each of the four corners of the parallelogram. However, as schematically illustrated in Figs. 2 and 3, commercial embodiments of the drive system may well utilize tough and resilient plastics materials from which the parallelogram linkage can be made in a single moulding, with living hinges 27,28,29 and 30 at respective corners, instead of separate pivot pins. Besides the advantages of cheapness of manufacture, the use of living hinges is attractive because it further reduces the number of separate moving parts of the drive system, with consequent reduced expectation of noise and vibration within the system.

It will also be noted that limbs 10 and 11 in Figs. 2 and 3 are not provided with central apertures for receiving pegs, as in the embodiment of Fig. 1.

Instead, lateral mounting pegs 31 and 32 are provided which are linked to the respective limbs 11 and 10 by further living hinges 33 and 34. Mounting pegs 31 and 32 will be received in correspondingly shaped recesses in the shaver body.

It will be appreciated that Fig. 2 illustrates the cutter drive in a central position, and Fig. 3 illustrates the drive in one extreme position.

In the normal case, as is shown in the drawings, the drive will be such as to create the same pitch of reciprocation on both of the cutters. However, there may be special situations, where a different pitch is desirable on each of the two cutters and this can readily be achieved by shifting the axis of reciprocatory rotation of the first pair of opposed links of the parallelogram linkage away from the mid-point of the limbs, in a direction towards the limb which carries the drive peg of the cutter which is to have a smaller pitch or wave length of reciprocatory movement.

Figs. 4,5 & 6 illustrate third embodiment of cutter drive. Figs. 4 and 5 show the drive in two extremes of motion, and Fig. 6 shows the drive in its central position. As in the embodiment of Fig. 1, the embodiment of Figs. 4 to 6 is constructed by linking the individual members together by means of pins.

Furthermore, the parallelogram linkage is attached to the body of the shaver by respective pins passing through apertures 181 and 191 on the transverse links 111 and 101.

The principal difference between the embodiment of Fig. 1 and the embodiment of Figs. 4 to 6 lies in the positioning of the eccentric drive pin and associated drive shaft. Whilst in the embodiment of Fig. 1 the drive shaft is located centrally of the parallelogram linkage, in Figs. 4 to 6 it is disposed laterally towards the bottom of the Figures. An eccentric drive pin 201 on the drive shaft is linked by a link member 202 to a further pin 203 provided on a flange 221 extending from the limb 13. It will be appreciated that such an off-centre drive arrangement may be convenient in certain circumstances to provide additional space within the shaver body for further components.

In all the illustrated embodiments it will be understood that the drive pegs 25 and 26 will engage with respective under-cutters of a reciprocatory type dry shaving unit. By use of the parallelogram linkage between the drive motor and the under-cutters, it is not essential that the axes of the foils should lie in a plane parallel to the plane of the parallelogram linkage. If desired, the plane tangential to the shaving foils may be at an angle to the plane of the parallelogram linkage. This angle may be as much as 450. This enables an angled shaving head to be provided, when necessary, in a relatively simple manner, whilst nevertheless providing appropriate drive to two counter-reciprocatory cutters.

Claims (11)

CLAIMS:

1. A dry shaver having first and second linear cutters mounted for counter-reciprocatory motion relative to the shaver body, drive means for driving the cutters; and a linkage for coupling the cutters to the drive means; characterized in that: said linkage comprises first and second pairs of opposed limbs forming a parallelogram arrangement; each limb of the first pair is mounted on the shaver body; each limb of the second pair provides a drive input to a respective cutter; and said drive means is arranged to cause oscillatory motion of the parallelogram linkage.

2. A shaver according to claim 1 wherein the drive means comprises a pin mounted eccentrically on a drive shaft extending from a drive source.

3. A shaver according to claim 2 wherein a drive flange is provided on a limb of said second pair for coupling to said pin.

4. A shaver according to claim 3 wherein said flange is provided with a slot receiving said pin.

5. A shaver according to claim 3 wherein said flange is linked to said pin by a pivotable link member.

6. A shaver according to any preceding claim wherein the first and second pairs of opposed limbs are coupled together by pivot joints.

7. A shaver according to any of claims 1 to 5 wherein the first and second pairs of opposed limbs are coupled together by living hinges.

8. A shaver according to any of claims 1 to 7 wherein each limb of said first pair is pivotally attached to the shaver body.

9. A shaver according to any of claims 1 to 7 wherein each limb of said first pair is attached by a living hinge to a support member secured to the shaver body.

10. A dry shaver substantially as hereinbefore described with reference to Fig. 1, Fig. 2 or Figs. 3 to 6 of the accompanying drawings.

11. Any novel feature or combination of features of the dry shaver hereinbefore described.