March 29, 1966 J. VAN DER DRBEST 3,

DRY SHAVER HEAD BIASED BY SPRINGS OF UNEQUAL STRENGTH Filed Aug. 28, 1964 7 13 1 19 5 1i 9 a l 18 1 INVENTOR.

JAN VAN DER DRIEST BY United States Patent 3,242,569 DRY SHAVER HEAD BIASED BY SPRINGS OF UNEQUAL STRENGTH Jan van der Driest, Drachten, Netherlands, assignor to North American Philips Company, Inc., New York, N .Y., a corporation of Delaware Filed Aug. 28, 1964, Ser. No. 392,700 Claims priority, application Netherlands, Sept. 13, 1963, 297,911 4 Claims. (Cl. 30-435) The invention relates to a shaving head for use in a dry shaving apparatus in which the shear plate together with the cutting member can be pressed inwardly against spring pressure into a terminal position determined by a stop.

The invention has for its object to improve the adaptability of shaving heads of this kind to the particular conditions of hair growth and skin of the users and is characterized in that a weak spring and a strong spring are connected in series.

With these constructions the user who Wants only a slight pressure for given parts of the skin surface or for the whole skin may employ solely the light pressure produced by depressing the light spring, since the series combination provides a distinctly perceptible change in spring pressure when the light spring has reached its operative terminal position and the stronger spring is depressed. At this instant a second pressure phase starts in which the pressure is determined by the depression of the stronger spring until the shear plate comes into contact with a stationary stop.

In this way the user obtains a satisfactory possibility of personal adaptation, while he can distinctly notice the transition from one pressure phase to the second phase and may utilize at will one of two spring pressure ranges without the need for carrying out a particular manipulation.

In constructions having a stationary shear plate it is already known to provide the driving coupling member for the moving cutter with a spring for pressing the cutter against the lower side of the plate, while the coupling member is loaded by a second spring. This does not concern a resilient depressibility of the shear plate together with the cutter in two pressure phases.

There are furthermore known various constructions in which use is made not only of springs for depressing the shear plate but also of separate springs which urge the cutter against the plate independently of the spring pressure exerted on said plate. This does not concern the stepwise actuation of two series-combined springs for shaving, at will, in different pressure phases either under the action of a weak spring or, upon further depression, under the action of a stronger spring connected in series with the former.

With a device in which the shear plate can be depressed together with the driven cutter, it is also known to provide an adjustability of the tension of the spring urging the driven cutter against the plate. This does not provide the effect aimed at by the invention.

The invention is preferably carried out so that the weak spring and the strong spring are arranged each on one side of a common, slidable cup spring. This provides a simple arrangement with a small number of parts while the transition from one phase to the other can be achieved simply by providing, at the side of the weak spring, in line with the driving spindle, a pivot with which the cup spring comes into contact when the weak spring is depressed.

The invention will now be described with reference to an embodiment shown in the drawing, however, further advantageous particularities will become evident.

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The figure shows an axial sectional view across the driving part of the rotating cutter of a dry shaving apparatus.

Against the shear plate 1, formed'by a cap, is urged a cutting member 2, formed by a cutter rim, in a resilient manner by the rotating spindle 3, the coupling being established in a known manner by means of a spring element 6 accommodated in a slot 5, the ends 7 of said ele-- ment being fixed in cavities of a hood 8 fastened to the cutter rim 2.

The stronger spring 10, lying in series with the weaker spring 9, is accommodated completely in the cavity 11 of the spindle 3, which itself is housed in a central hub cavity 12 of polyangular section of a rotating driving spindle 13 driven by means of a gear wheel (not shown).

The springs 9 and 10 are disposed each on one side of a common cup 14, which constitutes the bottom of a slidable element 15, adapted to slide in the cavity 11.

The weak spring 9 is wound helically on the sides of a pivot 16, which forms the end of a shaft 17, around which the driving spindle 13 is adapted to rotate. The spring 9 bears on the bottom part 18 of the cavity 12 in the spindle 13. It will be obvious that when the plate 1 is depressed during the shaving operation first the inward movement of the rotatable spindle 3 is transferred through a spring 10, which is not yet depressed, and via a cup 14 to the weak spring 9, which is thus depressed. The spring pressure to be overcome may amount to 60 gms. In the position shown in the drawing this pressure has been overcome so that the cup 14, which constitutes so to say a slidable bottom for the cavity 11 of the coupling member 13, bears on the end of the pivot 16. The stronger spring 10 is compressed between the upper wall of the cavity 11 and the cup 14 and so far the cup is thus held on a ridge formed by a ring 19 located in the cavity 11.

When the pressure of the shear plate 1 on the skin is increased, the spindle 3 slides along the element 15 in downward direction, and engages the ring 19 in its movement. The cup spring 14 is thus displaced inwardly into the cavity 11 and the spring 10 is depressed.

This can be continued until the lower edge 20 of the plate 1 comes into contact with the fixed stop 21 in the housing of the apparatus. The pressure on the shaving head then may have a value of 400 gms.

What is claimed is:

1. A shaving head for a dry shaver comprising a shear plate, a rotary cutter co-acting with said shear plate, a pair of springs of unequal strength arranged in line with each other and supporting said shear plate and rotary cutter whereby both are depressible against said spring pressure, a stop for arresting the movement of said shear plate and cutter in one direction, a slidable element having said springs engaging therewith on opposite sides thereof, and a fixed abutment against which said slidable element engages after a given compression of said weaker spring by a force applied to the shear plate of said dry shaver.

2. A shaving head for a dry shaver as claimed in claim 1 further comprising a spindle for driving said cutter, said spindle being arranged co-axially with said cutter, said springs being coil springs arranged co-axially with said cutter, and the latter being rotatable by said spindle through said springs.

3. A shaving head for a dry shaver as claimed in claim 1 wherein said fixed abutment comprises a fixed pivot arranged co-axially with said spindle, cutter and springs on that side of the slidable element which is adjacent to said weaker spring.

4. A shaving head for a dry shaver comprising a shear plate, a rotary cutter co-acting with said shear plate, a spindle having an axial cavity therein and being Patented Mar. 29, 1966 provided for driving said cutter, a pair of springs of unequal strength arranged in line with each other and supporting said shear plate and rotary cutter whereby both are depressible against said spring pressure, an abutment positioned on the wall of said cavity, a coupling member for transmitting the rotation of said spindle to said cutter, said coupling member being located in said axial cavity of the spindle and being movable axially therein as well as being rotatable with said spindle, the stronger of said springs being situated in said axial cavity and said coupling being provided with a movable member constituted of a cup being slidable axially in said cavity and engageable under the pressure of said stronger spring with said abutment on the wall of the cavity and 4- wherein said weaker spring is held between said cup and a part of said spindle and surrounds said pivot.

References Cited by the Examiner UNITED STATES PATENTS 2,416,776 3/ 1947 Schlotthauer 30-43.5

FOREIGN PATENTS 1,050,454 9/1953 France.

784,909 10/1957 Great Britain.

WILLIAM FELDMAN, Primary Examiner.

MYRON C. KRUSE, Assistant Examiner.