Pivotable hair cutting device for cutting over non-linear surfaces

A removable and replacable hair cutting head for use with motorized hair cutting tools. The hair cutting head adapts to conventional motorized hair cutting tool bodies allowing the head to pivot with a resistive bias through a limited range of angular motion. The cutting head itself has a non-linear array of cutting teeth for shearing hair over a non-linear surface. In the preferred embodiment, the cutting head has a longitudinal axis and is concave with respect to the longitudinal axis.

BACKGROUND OF THE INVENTION 
The present invention relates generally to hair cutting tools, and, more 
particularly, the invention relates to removable and replaceable 
actuatable cutting heads for electric hair cutting devices for use on a 
human head where the cutting head is non-linear and pivotable. 
Conventional electric hair cutting devices have an electrically motorized 
body and a cutting head. The cutting head is fixed with respect to angular 
motion and has a straight cutting surface. The cutting head attaches to 
the motor such that a reciprocating pin on the motor drives a lower blade 
on the cutting head against a fixed upper blade. A hair that is then 
placed in contact with the cutting head is sheared between the two blades. 
While conventional hair cutting devices do cut hair as intended, such 
systems do have certain limitations. For example, hair is generally found 
on non-linear surfaces such as the human head. The straight blades of the 
conventional system make only a portion of the blades usable when pressed 
directly against the human head. Faced with this problem, hair stylists 
often pull the hair away from the human such that only one end of the head 
is being used. Both of these procedures involve putting sharp points 
against the side of a head which can cause injury if the subject moves 
even the slightest amount. 
This same danger also exists if the electric cutter is being used to cut a 
straight line and the user is holding the cutter at an angle to the head. 
The angle will cause the end point of the cutting head to gouge the 
subject leading to a possible injury. 
Accordingly, it is an object of this invention to increase the usable area 
of the cutting head over a non-linear surface. 
It is another object of this invention to provide a device that simplifies 
cutting hair in a curved design. 
It is still another object of the invention to provide a safer cutting tool 
that is more adaptable to a cutting surface. 
These and other objects of the invention will be obvious and will appear 
hereinafter. 
SUMMARY 
The aforementioned and other objects are achieved by the invention which 
provides, in one aspect, a hair cutting tool. The invention provides an 
extremely versatile tool for cutting hair on a human head, or other 
surface containing hair. The system comprises a drive means and a cutting 
means. 
The drive means generates a drive force to power the hair cutting device. 
Often it is in the form of an elongate housing containing a motor. The 
motor drives a dive peg in a reciprocating motion to communicate the drive 
force axially from the drive means. 
The cutting means receives the drive peg and is actuatable by the drive 
force. The cutting means itself has a plurality of cutting edges 
reciprocating in shearing engagement, where each cutting edge has a 
non-linear array of cutting teeth for cutting hair that comes in contact 
with the cutting teeth. In the preferred form, the cutting means has a 
longitudinal axis and the non-linear array of cutting teeth are arced 
along said longitudinal axis relative to a centrally located axis. 
The cutting means is removably and replacably attachable to said drive 
means such that it can be used with conventional hair clipper bodies. The 
cutting means is made up of a stationary blade and a reciprocating blade. 
The stationary blade has a central pivot point to allowing angular motion 
with respect to the drive means. The angular motion of said stationary 
blade is mechanically limited to an angle of .+-.10.degree. in the 
preferred embodiment. In some instances a user may wish to lock the 
pivoting motion of the blades and, therefore, a push-pin is provided to 
fix the blades angular motion with respect to the drive means. 
The reciprocating blade is secured to the stationary blade such that the 
reciprocating blade is pivotable with the stationary blade. At the same 
time, the reciprocation blade is in communication with the drive means 
such that the reciprocating blade is driven in a reciprocating motion 
relative to the stationary blade. 
Another aspect of the blades is that the stationary blade has teeth of a 
first length and said reciprocating blade has teeth of a second length 
where the first length exceeds the second length. 
In further aspects, the invention provides methods in accord with the 
apparatus described above. The aforementioned and other aspects of the 
invention are evident in the drawings and in the description that follows.

DETAILED DESCRIPTION 
While the present invention retains utility within a wide variety of hair 
cutting devices and may be embodied in several different forms, it is 
advantageously employed in connection with a clipper for cutting hair on a 
human head. Though this is the form of the preferred embodiment and will 
be described as such, this embodiment should be considered illustrative 
and not restrictive. 
The invention is useful with a body supplying a drive force which is 
designed for use with the invention or is adaptable to any of various 
commercially available bodies for conventional cutting tools. 
The invention seeks to accommodate cutting non-linear cuts by allowing the 
cutting head of the tool to pivot about a central point with a limited 
allowable angular movement. Additionally, the blade of the cutting head is 
non-linear to conform more closely to the non-linear surfaces upon which 
the hair is found. 
FIG. 1 is a diagram of an assembled hair cutting tool according to the 
invention. The tool will be discussed as having two sections: a body 12 
and a head 10. The body 12 contains a drive mechanism which actuates the 
head 10 via a drive peg. The drive mechanism may be any of various 
devices, including a common electric motor (as depicted) or manually 
operated drive mechanism, but the drive mechanism will be referred to 
generally as the motor. 
The motor actuates the head 10 by communicating a drive force through the 
drive peg 14. The drive peg is reciprocally driven along an axis 
transverse to the plane of the drawing and along a cutting axis parallel 
to the cutting teeth of the head. In the preferred embodiment, the 
reciprocating motion of the drive peg is generated by a buzzer-type motor 
commonly known in the art or a rotary motor for quieter operation where 
the rotor motion is converted to linear motion by an eccentric and an 
eccentric cam as commonly known in the art. 
The reciprocating motion of the drive peg in this embodiment is 
pendulum-like in that the drive-peg follows a curve of substantially the 
same radius as the curve of the cutting surfaces. 
The head is made up of three sections: a lower cutting plate 20, a spacer 
plate 32, and an upper cutting plate 16. The lower cutting plate is 
connected to the drive peg 14 and is driven in a reciprocating motion 
along the cutting axis by the drive peg. On a top surface of the lower 
cutting plate and extending vertically are multiple track pegs 26. As the 
lower cutting plate 20 moves, the track peg follows a curved track 24 in 
the upper cutting plate forcing the lower cutting plate 20 to follow a 
curved path ensuring that the teeth of the lower cutting plate follow the 
teeth of the upper cutting plate 16. 
The spacer plate is located to the rear of the lower cutting plate and is 
fixed against a top surface of the body 12. In a forward area of the 
spacer plate 32 there is a pivot peg that extends vertically into a pivot 
recess in the upper cutting plate 16 for restricting a pivot motion of the 
upper cutting plate 16. 
The upper cutting plate 16 is pivotably attached through the spacer plate 
32 to the body 12 allowing the upper cutting plate 16 and the lower 
cutting plate 20 to have a limited angular movement with respect to the 
body 12. The limit of the angular movement is provided by the length of 
the angular recess 28 such that as the head pivots about the pivot screw 
36 the pivot peg remains stationary thereby stopping pivoting motion when 
it strikes the end of the pivot recess 28. 
Cutting by the curved cutting teeth is accomplished when the hair is placed 
between the teeth 18, 22 and the reciprocating motion of the drive pin 
causes the lower cutting plate 20 to slide along the stationary upper 
cutting plate severing the hair with a scissor-like action. 
FIG. 2 shows an exploded view of the cutting head as previously described. 
In this illustration the curved nature of the cutting teeth 18, 22 is 
readily seen. In the preferred embodiment, the radius of the curve of the 
teeth and the curved track approximate the curve of an average human head. 
The interconnections between the various sections of the cutting head 10 
are brought forward by this drawing. The spacer plate 32 is fixed to the 
body 12 by a plurality of screws 34. Also in this plate is illustrated a 
tapped pivot hole 38 into which the pivot screw 36 will be threaded. The 
pivot peg 30 extends vertically from the spacer plate to interconnect with 
the upper cutting plate 16. 
The lower cutting plate 20 is placed in front of the spacer plate 32 with a 
non-linear array of cutting teeth 22 extending axially at a distal end. 
The non-linear array of cutting teeth 22 are concave providing a curved 
cutting edge. In the preferred embodiment, the teeth themselves are coated 
with one of the following hard carbon, low friction carbide, tungsten, a 
diamond coating or molybdenum-disulfide to increase resistance to wear and 
decrease maintenance. 
The lower cutting plate sits over the drive peg previously described. The 
drive peg fits snugly into a drive slot 15. As the drive peg reciprocates 
along its curved path, the drive peg pushes against the sides of the 
drives slot communicating the drive force causing the lower cutting plate 
to reciprocate along the same path. Track pegs 26 extend vertically from 
the lower cutting plate into the curved track 24 further ensuring that the 
lower cutting plate follow the curved path. Additionally, the track pegs 
add lateral stability to the moving plate and reduce extraneous movements 
due to machining error or vibration. 
The upper cutting plate 16 is secured by the pivot screw 36 allowing a 
limited pivot as previously discussed and otherwise being fixed with 
respect to the lower cutting plate. 
There are numerous moving parts used in this invention which must be kept 
lubricated to ensure freedom of movement. Therefore, a lubricant must be 
chosen that is not susceptible to drying out and gumming and, therefore, 
will extend the time between cleanings. A lubricant with a low vapor 
pressure such as silicone oil may be used but such an oil tends to attract 
small particles. 
In the preferred embodiment, a dry lubricant is used to lubricate for 
long-term use. TEPHLON, a trademark owned by E.I. Dupont De Nemours, Inc., 
may be used, but molybdenum-disulfide (MoS.sub.2) is preferred due to the 
latter's ability to sustain in harsh environments. Therefore, at all 
frictional surfaces in the invention are coated with MoS.sub.2 in the 
preferred embodiment. 
FIG. 3 illustrates a second embodiment of the invention where a 
conventional commercially available body is used and a cutting head 
designed in accordance with the invention. The cutting head adapts to the 
body to replace a conventional cutting head with which the body was 
supplied. 
In this embodiment, an adapter plate 46 is attached to the motorized body 
to provide attachment points necessary for the pivoting motion of the 
cutting head. The adapter plate 46 is fabricated to be connected to the 
motorized housing 42 in a fixed position in the same way the conventional 
cutting head attached to the motorized body. In the illustrated example 
the way of attaching is two screws 56. 
The adapter plate allows the driver 44, which communicates a drive force 
from the motor, to pass through the adapter plate without restriction and 
connect directly with the lower cutting plate 64. 
FIG. 4 illustrates the interconnection of the individual parts of the 
cutting head, inter alia. The adapter screws 56 secure the adapter plate 
46 to the motorized body 42 while allowing the driver 44 to pass through a 
bore 48. Though this is the illustrated form of the adapter plate, 
numerous other methods of attachment and modifications of design may be 
employed to adapt the cutting head to various commercially available 
motorized bodies without departing from the inventive aspects of the 
invention. 
A spacer plate 50 is attached to the top surface of the adapter plate 46 
with spacer screws 58. The spacer screws are driven into threaded holes in 
the adapter plate to fix the spacer plate in position. 
A lower cutting plate 64 is placed over the remaining portion of the 
adapter plate such that the lower cutting plate 64 overlaps the adapter 
plate 46 extending the lower teeth 76 outward. 
The upper cutting plate 72 is then secured over the spacer plate 50 and the 
lower cutting plate 64. A single pivot screw passes through a hole in the 
upper cutting plate and through a slot 60 cut into the lower cutting plate 
into a threaded hole in the adapter plate. The hole in the upper cutting 
plate is unthreaded to accommodate free movement and may be lined with a 
bearing to further promote such movement. The slot 60 is wide so as not to 
hinder the reciprocating motion of the lower cutting plate. 
Having been secured by the pivot screw 62 in such a way as to allow angular 
movement parallel to the plane of the adapter plate, the cutting head can 
now move with the contour of the surface over which it is cutting. The 
angular movement is restricted by a pivot pin 52 that extends vertically 
from the spacer plate 50 into a pivot bore 54 such that the head is 
restricted to a useful cutting range and the linear motion of the drive 
peg is not being forced to drive the cutting head at too great an angle to 
properly transfer the drive force. In the preferred embodiment, the angle 
is restricted to .+-.10.degree.. 
The sides of the pivot bore are lined with a foam rubber to bias the 
cutting head 43 toward a normally centered position while adding a 
steadily increasing bias away from sides. If necessary, opposing springs 
may also be used to increase to normally centered bias where the foam 
rubber pad would then be used for damping the pivot motion. 
In either of the two embodiments, a push-pin (not shown) may be added to 
optionally fix the pivoting motion of the cutting head. The push-pin would 
normally be extended vertically from the upper cutting plate. If the user 
chose to fix the pivotability of the cutting head, downward force would be 
applied to the top of the push-pin forcing it to extend down through the 
upper cutting plate into the spacer plate of the adapter plate. Upon 
completion of the task requiring a fixed cutting head, the push-pin would 
be raised by the user pulling up on the push-pin or other ejection method 
commonly found in the art. 
The upper teeth 74 extend outward over the lower cutting plate 64 and 
slightly beyond. The upper teeth themselves are longer than the lower 
cutting teeth 76 to avoid pulling hairs. It accomplishes this by allowing 
the upper cutting teeth to comb the hair into the lower cutting teeth 
where the hair is sheared by the reciprocating motion of the lower cutting 
teeth. 
The upper cutting teeth 74 and the lower cutting teeth 76 are curved inward 
and concave with respect to a plane transverse to the pane of the adapter 
plate. The concave nature of the cutting teeth allow the cutting head to 
move over a nonlinear surface without gouging at the edges. 
In an alternative embodiment (not shown), the curve of the teeth arcs 
creating a convex shape relative to the plane of the adapter plate. This 
curvature is useful in certain circumstances for cutting hair non-linearly 
around fixed objects, such as cutting the hair around an ear. 
The invention may be embodied in other specific forms without departing 
from the spirit or essential characteristics thereof. The present 
embodiments are, therefore, to be considered in all respects as 
illustrative and not restrictive, the scope of the invention being 
indicated by the appended claims rather than by the foregoing description, 
and all changes which come within the meaning and range of equivalency of 
the claims are therefore intended to be embraced therein.