Hair trimmer

The present invention is a cutting unit having multiple sets of tandem blades; each set being composed of a first toothed blade moved reciprocatingly in a cutting motion relative to a second tooth blade. The blades are preferably curved.

BACKGROUND OF THE INVENTION 
1. Field of the Invention. 
The present invention relates generally to cutting units and more 
particularly to a hair trimmer. 
2. Description of the Prior Art. 
There are numerous cutting units known in the art. One type of unit 
utilizes a reciprocating tooth blade moving relative to a second blade. 
The blades are aligned substantially longitudinally of the device and its 
handle. When this arrangement is utilized in a hair trimmer, the device 
can be conveniently used by an untrained individual because the 
orientation of the blades is similar to that of a comb. Using blades with 
a curved cutting edge further facilitates trimming and proper shaping of 
the hair. 
Disadvantageously, as is known in the art, see e.g. U.S. Pat. No. 4,214,365 
to Walter, et al., when these reciprocating cutting units have a high 
motor and blade speed the noise is a deterrent to its use. When low motor 
and blade speeds are utilized, the motor noise factor may be reduced, but 
the sickle bar or mowing-machine noise of the blade remains, particularly 
if the blade is long. 
These units also have relatively high costs and complex constructions which 
make assembly, repair and cleaning difficult. A major factor in the cost 
is the fabrication of a long moveable cutting blade. The dimensions of a 
long, moveable blade require exactitude in fabrication since improper 
frictional contact with the second blade is capable of producing a 
substantial noise when reciprocated and increased wear and tear on cutting 
components. A curvature in a long cutting blade further increases its 
cost. Prior art reciprocating cutting units have not been entirely 
satisfactory, with respect to noise, maintainability and cost. 
It is, accordingly, an object of the present invention to provide an easily 
manipulated, efficient, quiet, hair trimmer having relatively few 
components that is particularly well-adapted for self-use. 
It is an additional object of the present invention to provide a hair 
trimmer which can be drawn through a bed of hair in a combing motion while 
shearing off hair segments. 
It is a further object of the present invention to provide a hair trimmer 
having a cutting unit with multiple aligned curvate cutting blades which 
are coupled for simultaneous reciprocation. 
It is also an object of the present invention to provide a hair trimmer 
having multiple cutting blades which are aligned to form a curvature in 
their cutting edges approximating the curvature of the human head. 
SUMMARY OF THE INVENTION 
These objects and features are accomplished by the present invention 
wherein a cutting unit comprises the following: a cutting assembly 
including multiple sets of tandem blades, each set having a separate first 
toothed blade bearing against, and slideable along, an adjacent second 
toothed blade in a reciprocating cutting motion, the first blade of the 
multiple sets being longitudinally aligned and coupled for simultaneous 
reciprocating motion relative to the second blade of each set, and 
reciprocating means for producing said reciprocating motion in said first 
set of blades. There is preferably a support plate adjacent the second 
blade in each set which is fixedly secured in a stationary position by 
attachment, direct or indirect, to the housing. 
In cutting units used for hair trimming, a hand holdable casing is provided 
having a longitudinal slot permitting the teeth of the tandem blades to 
extend out of the casing. The tandem blades are curved, aligned and 
complimentary so as to form a curvature approximating that of the human 
head.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the Figures, wherein an electric powered hair trimmer, 
referred to generally by reference numeral 10, includes a hollow casing 
11, formed from molded first and second sections, 12a and 12b, 
respectively, rigidly secured together by screws 13. The casing 11 
includes a handle portion 16 and a cutting portion 18. The handle portion 
16 provides a convenient hand grip for either a left or right hand user. A 
slide switch 20, mounted on top of the casing 11, is finger actuatable for 
energizing a cutter assembly 21 through switch means 19. The cutter 
assembly 21 is disposed within the casing 11 and accessible for 
maintenance through door 20a. The handle portion 16 has inner walls 17a, 
17b integrally molded with the sections 12a and 12b, respectively, which 
provide support to parts of the cutter assembly 21 and minimize 
undesirable movement within the casing 11. The cutting portion 18 has a 
longitudinal slot 22 permitting access to the cutter assembly 21 
therethrough. Bordering the slot 22 is a recessed groove 23 which is 
slidably accessible from end 24 and which permits attachment to 
accessories such as a comb 28a or shaver 28b having portion 28c mating 
with the recessed groove 23. The comb 28a controls the depth of 
penetration of the blades of the cutter assembly 31 into the hair. The 
shaver 28b accessory exposes the blades to a greater degree than the comb 
28a and is particularly useful for close trimming. 
The cutter assembly 21 includes a motor 25 for producing rotary motion, 
reciprocating means 30 for converting rotary motion into reciprocal 
motion, and cutting means 31 for converting the reciprocating motion to a 
cutting motion. 
The motor 25 is energized by low voltage D.C., supplied through an adaptor 
(not shown), cord 25a, jack 25b, or battery (not shown). The motor 25 
produces a high rpm and has a housing 26 and a bearing portion 27 with a 
rotatable output shaft 29 extending therefrom. 
The reciprocating means 30 includes a gear housing assembly 32, a cam-gear 
assembly 36, a cluster gear 38 rotatably secured to the casing 11, a 
pinion gear 40, and a drive extension 42. 
Secured to the bearing portion 27 is the gear housing assembly 32. This 
assembly 32 includes a motor mounting yoke 43, a flat portion 45 with an 
aperture 47 to receive the bearing portion 27 of the motor 25 and a 
forward extension 49. A U-shaped portion 51 of the motor mounting yoke 43 
engages the housing 26 of the motor 25. The yoke 43 is formed from a 
spring grade wire and has opposed legs 55a, 55b extending forwardly on 
opposite sides of the motor 25 and through opposite slots 56a, 56b, 
respectively, in the flat portion 45. The legs 55a, 55b each have 
transverse bends 63, extending towards each other and terminating in 
rearward extending pin ends 64 which are receivable in a pair of apertures 
65 adjacent the slots 56a, 56b. The motor 25 is positioned and supported 
against rotation by the snug fit of the bearing portion 27 in the aperture 
47, tension on the yoke 43 and the sandwiching of the flat portion 45 
between inner wall extensions 62a, 62b on inner wall 12a and opposing wall 
extensions (not shown) on inner wall 17b. 
Mounted over and around the output shaft 29 is the forward extension 49 of 
the gear housing assembly 32, which includes a generally cylindrical 
chamber 68 formed as an extension of the aperture 47, and an axle 
extension 69 having a bore 70 which is co-axial with the shaft 29. The 
forward extension 49 is partially cut away along the cylindrical chamber 
68 to provide access to pinion gear 40 mounted on the motor shaft 29. 
The cluster gear 38 has a lower larger gear 38a and smaller upper gear 38b 
mounted on a pin 74 pressed into a recess 75 in the flat portion 45 of the 
gear housing assembly 32, and located to provide engagement of the larger 
gear 38a with the teeth 71a of the pinion gear 40. The smaller gear 38b is 
positioned to engage the internal teeth 72 of ring 81 of the integral 
cam-gear assembly 36, which is journalled on a pin 80 pressed into a 
recess in the axle extension 69. The pinion 40, cluster gear 38, and 
internally toothed ring 81 form a gear reduction train which reduces the 
speed of the output shaft 29 to provide a speed range suitable for moving 
the blades for cutting. 
The cam gear assembly 36, mounted over the gear housing assembly 32, 
includes the ring 81, a barrel cam 83 extending from and integral with the 
ring 81, and pin 80. The ring 81, as mentioned, has internal teeth 72 
which is engaged by the larger gear 38a so as to rotate the ring and 
barrel-cam unit 81, 83. This unit 81, 83 is journalled on the pin 80 and 
is retained thereon at one end by a washer 82. The pin 80 extends through 
a bore 84 in the barrel cam 83 into the aligned bore of the axle extension 
69 where it is secured. The barrel cam 83 has an external surface 87 with 
a wobbled circumferential groove 89. A hair guard 90 prevents the hair 
segments sheared by the cutter assembly 21 from jamming the operation of 
the barrel-cam unit 81, 83. 
The drive extension 42 has a skirt portion 88 and an elongated portion 93 
extending therefrom. The elongated portion 93 is secured to the cutting 
means 31, as described hereinafter, so as to be restrained against 
rotational movement while permitting reciprocating axial movement to be 
transmitted from the drive extension 42. The skirt portion 88 has an inner 
wall 92 with a cam follower 94 extending inwardly therefrom so as to 
engage the circumferential groove 89. The groove 89 has a continuous path 
which, during rotation of the gear housing assembly 32 by the cluster gear 
38, is traversed by the cam follower 94 so as to move the drive extension 
42 in a sinusoidal reciprocating motion and drive the elongated portion 93 
in a reciprocating motion. 
The elongated portion 93 has a first and second pin receiving aperture 91a 
and 91b, respectively, for engaging the cutting means 31, as hereinafter 
described. The first aperture 91a is intermediate the length of the drive 
extension 42 and has a center line offset from that of the extension 42, 
while the second aperture 91b has a coinciding center line. 
The cutting means 31 includes an inner support plate 95, an outer retaining 
spring 97 and a first and second identical set of tandem blades 99 
therebetween, separated by a gap 100; each set includes a stationary blade 
101 and a moveable blade 103. Each of the moveable blades 103 are 
identical with the others, and each of the stationary blades are identical 
with the others. 
The support plate 95 is fixedly secured to the inner wall of the casing 11 
by screws 105 and has an opening 107, a recess 109, an inner surface 110, 
an outer surface and a lower surface 114. The lower surface 114 has a 
curvature approximating that of the human head. Projecting from the planar 
inner surface 110, and disposed thereon so as to describe a curved path 
having a slightly smaller radius of curvature than the curved edge 114, 
are two pairs of pin rivets 116. 
Mounted on each pair of rivets 116, and adjacent to the support plate 95 is 
a stationary blade 101; each having a flat portion 118 bearing against the 
support plate 95 and an offset portion 119 projecting beyond the lower 
surface 114. 
Each moveable blade 103 is mounted adjacent a stationary blade 101 and has 
a bottom planar toothed portion 122, a top planar portion 124 and an 
offset portion 120 therebetween. The offset portion 120 has two elongated 
apertures 128; each aperture having dimensions permitting the moveable 
blades 103 to slide reciprocably about the pair of pins 116 and along the 
corresponding stationary blade 101. Each offset portion 120 does not 
contact a stationary blade 101; this arrangement minimizing friction and 
wear and tear on the cutting components. Each bottom planar toothed 
portion 122 and top planar portion 124 bears against the corresponding 
portion of the stationary blade 101. The bottom portion 122 has similarly 
sized teeth having tips which define a blade edge curvature having a 
slightly smaller radius than that of each stationary blade 101. 
Each top portion 124 has a riveted pin 127 extending inwardly. One pin 
extends through the opening 107 and engages the first pin-engaging 
aperture 91a, while the other pin extends through the recess 109 and 
engages the second aperture 91b. The dimensions of opening 107 and recess 
109 are such that the support plate 95 does not interfere with the motion 
of each of the rivet pins 127. 
The width of each moveable blade 103 is less than that of the adjacent 
stationary blade 101, and the reciprocating motion moves each moveable 
blade 103 cyclically and repetitively from one substantially vertical end 
104a of the corresponding stationary blade to the other substantially 
vertical end 104b simultaneously. 
Mounted on each pair of pin rivets 116, and forcing the blades of each 
tandem set 99 against each other is a retaining spring 97 locked thereon 
by washers 132. Each spring 130 has a first and second pressure producing 
spring arm 140, 142, respectively. The arms 140, 142 supply a bearing 
pressure to the bottom and top portions of the moveable blade 103 so as to 
maintain the moveable blades in slideable contact with the stationary 
blade 101. 
The hair trimmer is operated by moving the slide switch 20 to on and 
activating the motor 25 which turns the output shaft 29 and the attached 
pinion gear 40. The pinion gear 40 rotates the cluster gear 38, with the 
smaller gear 38b rotating the barrel-cam gear assembly 36 and driving the 
elongated portion 93 of the drive extension 42 in a reciprocating motion. 
This motion is transmitted to the coupled, aligned, curved and moveable 
blades 103 which cooperate with the curved stationary blades 101 so as to 
shear hair drawn between their teeth when moving the cutting portion 18 
through a bed of hair.