Cutting head assembly for hair trimmers

A cutting head selectively engageable with a first support tongue having by a pair of ribs disposed on the bottom of the tongue, and selectively engageable with a second support tongue having a substantially planar bottom surface, the cutting head comprising a bottom plate having an upper surface, an upper plate supported by the upper surface, a spring fixed to the bottom plate for biasing the upper plate against the upper surface, and a single tongue-receiving socket for snugly receiving the first support tongue and for snugly receiving the second support tongue.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The invention relates to electric hair trimmers, and more particularly to 
cutting head assemblies for use with electric hair trimmers. 
2. Related Prior Art 
It is generally known to provide an electric hair trimmer with a cutting 
head assembly which can be releasably and operably mounted on the trimmer. 
The provision of a releasable cutting head assembly facilitates the 
cleaning and replacement of the cutting head assembly. Typically, an 
electric hair trimmer for use with a releaseable cutting head assembly 
includes a body and a spring-loaded, pivotable support tongue which is 
fixed to one end of the clipper body. The support tongue is engageable 
with the associated cutting head assembly to hold the cutting head 
assembly in an operable position on the clipper body. When the tongue is 
pivoted forwardly to an "open" position away from the body, the cutting 
head assembly can be placed on the tongue. When the tongue is snapped into 
a "closed" position against the clipper body, the cutting head assembly is 
held securely against the clipper body. 
Two examples of releaseable cutting head assemblies for use in association 
with a hair trimmer are illustrated respectively in U.S. Pat. No. 
2,182,597 which issued to Oster on Dec. 5, 1939, and in U.S. Pat. No. 
2,928,171 which issued to Oster on Mar. 15, 1960. The above-listed U.S. 
Patents illustrate cutting head assemblies which include a 
tongue-receiving socket for mounting the assembly on an associated support 
tongue. 
Under some circumstances, it may be desirable for cutting head assemblies 
to be interchangable between various electric clippers. Some cutting head 
assemblies cannot be interchangably mounted on some trimmers, however, 
because some trimmers provide a support tongue which has a specific 
configuration and which can only releasably engage a particular cutting 
head assembly having a correspondingly configured tongue-receiving socket, 
but which cannot releasably engage a cutting head assembly having a 
differently configured tongue-receiving socket. 
For example, one type of support tongue known in the prior art has a 
relatively uniform thickness across the width of the tongue and has a 
generally planar bottom surface. Another type of support tongue known in 
the prior art has a varying thickness across the width of the tongue and 
is characterized by two ribs which are disposed on the bottom surface of 
the tongue and which extend downwardly. A cutting head assembly configured 
for use in association with a trimmer having the first type of support 
tongue, i.e. a tongue having a generally planar lower surface, cannot be 
used interchangeably with a trimmer having a support tongue including a 
ribbed bottom surface because the downwardly extending ribs prevent 
engagement of the tongue with the tongue-receiving socket. 
SUMMARY OF THE INVENTION 
One of the features of the invention is the provision of a cutting head 
assembly which can be releasably engaged with various support tongues 
having differing configurations. 
Another feature of the invention is the provision of a cutting head 
assembly which can be releasably engaged with a support tongue having a 
generally planar lower surface as well as with a support tongue having 
ribs disposed on the bottom surface of the support tongue. 
The invention also provides a cutting head assembly including means 
defining a single tongue-receiving socket for receiving a support tongue 
on an electric hair trimmer. The socket is adapted to receivably engage 
various support tongues having different configurations, and is adapted to 
releasably and operably mounting the cutting head assembly on the body of 
an electric hair trimmer. 
In one embodiment, the tongue-receiving socket has a relatively uniform 
height across the width of the socket, and includes means extending 
inwardly of the socket to diminish the height of the socket at the ends of 
the socket. In one embodiment of the cutting head assembly, the 
tongue-receiving socket is defined by a bottom plate and a U-shaped strap 
which is fixed to the bottom plate and which has a central portion which 
is spaced away from the bottom plate. The means extending inwardly of the 
socket to diminish the height of the socket at the ends of the socket 
includes a pair of tabs which are fixed to the bottom plate and which 
extend under the ends of the central portion of the strap. 
It is contemplated that the socket will snugly receive the type of support 
tongue having a planar bottom, as well as the type of support tongue 
having a ribbed bottom. When mounted on an electric hair trimmer having a 
support tongue with a planar lower surface, the socket engages the support 
tongue in a relatively snug manner so that the upper surfaces of the tabs 
engage the bottom surface of the tongue and the remainder of the socket 
envelopes the tongue so that when the support tongue is pivoted to a 
"closed" position against the clipper body, the cutting head assembly is 
securely and operably mounted on the electric clipper. 
When mounted on an electric hair trimmer having ribs disposed on the bottom 
surface of the support tongue, the socket snugly receives the support 
tongue so that the upper surfaces of the tabs engage the bottom surface of 
the tongue and the inner ends of the tabs engage the sides of the ribs. 
Various other features and advantages of the invention will become apparent 
to those skilled in the art upon review of the following detailed 
description, claims and drawings.

Before one embodiment of the invention is explained in detail, it is to be 
understood that the invention is not limited in its application to the 
details of construction and the arrangements of components set forth in 
the following description or illustrated in the drawings. The invention is 
capable of other embodiments and of being practiced or being carried out 
in various ways. Also, it is to be understood that the phraseology and 
terminology used herein is for the purpose of description and should not 
be regarded as limiting. 
DESCRIPTION OF THE OF THE PREFERRED EMBODIMENT 
Illustrated in FIG. 1 is an electric hair trimmer 10 having a body 12 which 
is formed to be easily hand-held. The body 12 houses an electric motor 14 
which is connected to a suitable source of current 16 which, as shown 
schematically in FIG. 1, can be in the form of a battery. However, the 
trimmer body could also support an electric cord for connection with a 
suitable source of current. A user operable switch 18 for turning the 
electric motor 14 "on" and "off" extends from the clipper body 12. A 
rotatable drive shaft 20 extends from the electric motor 14 to an end 21 
of the clipper body 12 which supports a cutting head assembly 22. The 
drive shaft 20 supports an eccentrically mounted cam 24 which, when 
rotated, imparts a reciprocating motion to a drive lever 26 which extends 
from the clipper body 12 and which, in turn, operably engages the cutting 
head assembly 22. 
The hair trimmer 10 also includes mounting means 28 supported on the end 21 
of the clipper body 12 for releasably engaging the cutting head assembly 
22. While various features of the mounting means 28 are described herein, 
U.S. Pat. No. 2,182,597, which issued to Oster on Dec. 5, 1939, also 
describes means for readily removably attaching a cutting head assembly to 
a clipper body and for holding the cutting head assembly in place thereon. 
In the disclosed embodiment, the mounting means 28 includes (FIG. 2) a 
base plate 30 which is fixed to the end 21 of the clipper body 12 by a 
pair of: screws 32. The base plate 30 carries a pair of laterally spaced 
arms 34 which are curled to form a pair of hinge loops 36. A central 
portion 38 of the base plate 30 extends outwardly from the end 21 of the 
clipper body 12. A pair of side flanges 40 extend upwardly from the 
central portion 38 to either side of the drive lever 26. 
As shown in FIG. 1, a hinge pin 42, which extends through the hinge loops 
36, hingedly mounts a support tongue 44 in a position overlying the base 
plate 30. In the illustrated embodiment, the support tongue 44 is mounted 
on the clipper body 12 for pivotal movement from an "open" position (shown 
in phantom) wherein the tongue 44 extends forwardly away from the clipper 
body 12 to a second "closed" position wherein the tongue is held next to 
the clipper body 12. The mounting means 28 also provides a spring 46 which 
engages one end of the tongue 44 and the base plate 30 for holding the 
tongue 44 in either the "open" or "closed" position. 
The support tongue 44 may take the form of various configurations. One type 
of support tongue 44 shown in FIGS. 2 and 9 has an upper surface 50, a 
generally planar lower surface 52, opposite edges 54, and has a relatively 
uniform thickness. The support tongue 45 shown in FIGS. 3 and 7, has an 
alternative configuration including an upper surface 50, a lower surface 
52, opposite edges 54, and a pair of ribs 56 disposed on the lower surface 
52 and extending generally parallel to and being spaced from the opposite 
edges 54. Because the ribs 56 extend downwardly from the lower surface 52 
of the ribbed support tongue 45, the support tongue 44 has an overall 
thickness which is greater than the thickness of the support tongue having 
a plannar bottom surface. While the alternative configurations of the 
support tongues 44, 45 have various different overall thicknesses, the 
alternative configurations typically have a standard width, i.e. the 
distance between the opposite edges 54 is the same for the alternative 
configurations of support tongue 44 and 45. 
The above-mentioned cutting head assembly 22 includes (FIGS. 2 and 4) a 
bottom plate 62 having an upper surface 64 and a lead edge 66 
characterized by a set of teeth 68. The upper surface 64 of the bottom 
plate 62 supports a top plate 70 for reciprocal sliding movement relative 
thereto. The top plate 70 has an edge 72 characterized by a second set of 
teeth (not shown) which cooperate with the set of teeth 68 on the bottom 
plate 62 to cut hair when the top plate 70 is reciprocated relative to the 
bottom plate 62. The top plate 70 defines a rearwardly opening channel 76 
which is adapted to engage the drive lever 26 and is reciprocally driven 
by the drive lever 26. 
The cutting head assembly 22 also includes (FIG. 2) spring means 78 for 
biasing the top plate 70 against the bottom Plate 62. In the preferred 
embodiment, the spring means 78 is a leaf spring 80 which includes a bight 
portion 82 positioned on the top plate 70 and two legs 84 extending 
rearwardly from the bight portion 82 to form therebetween a U-shaped space 
86. While other arrangements can be used, in the disclosed embodiment, 
each leg 84 includes a curled portion 88 which extends under the leg 84 
and terminates in an end 89 which is fixed to the upper surface 64 of the 
bottom plate 62. The leaf spring 80 biases the top plate 70 against the 
upper surface 64 of the bottom plate 62 to maintain sufficient pressure 
therebetween for effective cutting. 
In order to provide a cutting head assembly which is interchangable between 
electric hair trimmers having differing support tongue configurations, the 
cutting head assembly 22 (FIG. 5) provides means 90 defining a single 
tongue-receiving socket 91 for selectively and receivably engaging a 
support -tongue 44 having a generally planar bottom surface 52 (FIGS. 10 
and 11), and for selectively and receivably engaging a support tongue 45 
having ribs 56 disposed on the bottom surface 52 of the support tongue 
(FIGS. 8 and 12). While various other constructions could be used, in the 
illustrated embodiment, the socket defining means 90 includes (FIG. 5) the 
above-mentioned socket 91 which is defined by a pair of spaced-apart end 
walls 92, a bottom wall 94 and a top wall 96. A generally U-shaped strap 
98 extends between the legs 84 of the spring 80 and defines the top wall 
96 of the tongue-receiving socket 91. The strap 98 has opposite ends 100 
and a central portion 102 which extends between the opposite ends 100 and 
which is spaced from the upper surface 64 of the bottom plate 62. As shown 
in FIG. 4, the opposite ends 100 of the strap 98 are fixed to an end 89 of 
a respective leg 84 of the leaf spring 80 so that the curled portions 88 
of the spring 80 extend over the ends 100 of the strap 98. While not shown 
in the drawings, the strap 98 could also, for example, be fixed directly 
to the upper surface 64 of the bottom plate 62. Each end 100 of the strap 
98 includes (FIGS. 2 and 5) a bent portion 104 which curves upwardly from 
the leg 84 of the spring 80 to the central portion 102 of the strap 98. 
The bent portions 104 provide a clearance between the upper surface 64 of 
the bottom plate 62 and the strap 98 which is greater than the thickness 
of the legs 84 of the spring 80. The ends 89 of the legs 84 and the bent 
portions 104 thus define the spaced-apart end walls 92 of the socket 91. 
Because the various configurations of the support tongue 44 have a standard 
width, the end walls 92 are preferably spaced-apart, as indicated by 
dimension L in FIGS. 4 and 5, to correspond to the standard width of the 
support tongues. 
As shown in FIG. 11, a pair of alignment flanges 106 extend upwardly from 
the central portion 102 of the strap 98. The alignment flanges 106 nest 
with the side flanges 40 on either side of the drive lever 26 to securely 
position the cutting head assembly 22 when the support tongue 44 is 
snapped into the closed position. 
The socket defining means also includes (FIG. 1) a portion 108 of the upper 
surface 64 of the bottom plate 62 which extends between the legs 84 of the 
spring 80 and which defines the bottom wall 94 of the tongue-receiving 
socket 91. As shown in FIG. 5, the central portion 102 of the strap 98 and 
the portion 108 of the bottom plate 62 are relatively uniformly 
spaced-apart so that the socket has a substantially uniform height. 
The cutting head assembly 22 also includes (FIG. 5) means 110 extending 
inwardly of the socket 91 from the end walls 92 for diminishing the height 
of the socket 91 at each end of the socket 91. While various arrangements 
could be used, in the illustrated embodiment, the means 110 extending 
inwardly of the socket 91 to diminish the height of the socket 91 includes 
a pair of tabs 112. Each tab 112 is integrally formed on a leg 84 of the 
spring 80 and extends inwardly of the socket 91. Thus, the ends 100 of the 
strap 98 are respectively fixed to the pair of tabs 112. In the preferred 
embodiment, each tab 112 has a thickness substantially equal to the 
thickness of the legs 84. Because of the upwardly extending bent portions 
104 of the strap 98, the central portion 102 of the strap 98 is spaced 
from the upper surface 114 of each tab 112. The bent portions 104 of the 
strap 98 provide sufficient clearance between the upper surface 114 of the 
tabs 112 and the central portion 102 so that the edges 54 of a support 44 
tongue can be snugly and slideably received therebetween. The innermost 
ends 116 of the tabs 112 terminate in rib engaging surfaces which are 
spaced-apart so that the ribs 56 on the lower surface 52 of a support 
tongue 44 can be snugly and slideably received therebetween. 
As shown in FIGS. 10 and 11, the socket 91 is adapted to receive the 
relatively thin support tongue 44 such that the plannar lower surface 52 
of the tongue 44 is received on the upper surface 114 of the tabs 112 and 
is held snugly by the strap portion 98 and the bent portions 104 of the 
strap 98. The socket 91 is also adapted to receive a support tongue having 
ribs 56 disposed on the lower surface 52 of the tongue 44. As shown in 
FIGS. 8 and 12, the ribbed tongue 45 can be snugly received by the socket 
91 such that the inner ends 116 of the tabs 112 engage the sides of the 
ribs 56, the lower surface 52 of the tongue 44 extends over the upper 
surface 114 of the tabs 112, and the upper surface 50 of the tongue 44 is 
snugly received by the strap portion 98. The socket 91 defining means thus 
provides a cutting head assembly 22 which snugly receives alternative 
embodiments of known support tongues and is interchangeable between hair 
trimmers having support tongues of various configurations. 
Various features of the invention are set forth in the following claims.