U.S. patent number 3,902,498 [Application Number 05/447,577] was granted by the patent office on 1975-09-02 for surgical cutting instrument.
This patent grant is currently assigned to Minnesota Mining and Manufacturing Company. Invention is credited to Peter G. Niederer.
United States Patent |
3,902,498 |
Niederer |
September 2, 1975 |
Surgical cutting instrument
Abstract
A surgical instrument with a first cutting member having a
passage therein and a second cutting member slidably received
within the passage. A storage recess formed in said passage by the
second cutting member has an inlet opening and a discharge opening
with the first and second cutting members having a configuration
that provides a cooperative shearing action between the members
during relative movement of the members in a first direction with
sheared material being deposited in the storage recess through the
inlet. Means are provided to cause movement of the sheared material
within the recess toward the discharge opening during relative
movement of the members in a second direction with means also being
provided to cause the relative movement of the cutting members in
said first and second directions. A replaceable cutting tip for a
surgical instrument with the replaceable tip having a cutting tip
body of an elongated generally cylindrical configuration. The body
includes a longitudinal bore, a forward end, a rearward end, and a
knife edge defined by the forward end. Means are provided to engage
cut material within the bore during movement of the tip body in a
second direction to move the material in the direction of movement
of the cutting tip body. During movement of the cutting tip body in
a first direction, the cut material is disengaged and there is
movement of the body with respect to cut material within the bore.
Means may also be provided to position the cutting tip with its
rearward end in engagement with a surgical instrument and with the
means to engage and disengage cut material within the bore being
fixed in a desired position with respect to the surgical
instrument.
Inventors: |
Niederer; Peter G. (Goleta,
CA) |
Assignee: |
Minnesota Mining and Manufacturing
Company (St. Paul, MN)
|
Family
ID: |
23776887 |
Appl.
No.: |
05/447,577 |
Filed: |
March 4, 1974 |
Current U.S.
Class: |
606/170 |
Current CPC
Class: |
A61B
17/1611 (20130101); A61B 2017/00539 (20130101) |
Current International
Class: |
A61B
17/32 (20060101); A61B 17/00 (20060101); A61B
017/32 () |
Field of
Search: |
;30/130,228,241,242
;128/305,310,312,318 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pace; Channing L.
Attorney, Agent or Firm: Alexander, Sell, Steldt &
DeLaHunt
Claims
I claim:
1. A surgical cutting instrument comprising:
a first cutting member having a passage therein;
a second cutting member slidably received within said passage;
a recess in said second cutting member;
said passage having an inlet opening and a discharge opening;
means to cause relative movement of said members in first and
second directions;
said first and second cutting members having a configuration for
cooperative shearing action upon bone or tissue located between
said members at an operation situs during relative movement of said
members in a first direction, said cooperative shearing action
causing sheared bone or tissue material to be deposited in said
recess and into said passage through said inlet opening;
means to cause movement of said sheared bone or tissue material
within said recess and passage toward said discharge opening during
relative movement of said members in a second direction; and
said discharge opening being spaced from said inlet opening such
that said sheared bone or tissue material ejected through said
discharge opening is displaced from the operation situs.
2. A surgical tool according to claim 1 wherein the means to cause
movement of said sheared bone or tissue material within said
passage toward said discharge opening during relative movement of
said first and second cutting members in a second direction
comprises a smooth slide surface in said recess and a frictional
surface within said passage, said frictional surface and said
smooth slide surface cooperating to engage sheared bone or tissue
material therebetween to thereby move said sheared bone or tissue
material in said recess and passage toward said discharge opening
during relative movement of said first and second cutting members
in said second direction.
3. The surgical tool of claim 2 wherein said frictional surface
comprises a serrated surface directionally biased to engage sheared
material during relative movement of said cutting members in said
second direction and to disengage the sheared material during
relative movement of said cutting members in said first
direction.
4. The surgical tool of claim 1 wherein
said first cutting member is movable and said second cutting member
is fixed;
said first cutting member having a generally elongated
configuration, an outer end, a knife edge on said outer end, with
said passage positioned generally axially of said first cutting
member;
said second cutting member having a generally elongated
configuration and an outer support surface conforming to the
surface of said passage and slidably engaging said passage in
supporting relationship with said first cutting member;
said second cutting member having an outer end which defines a
gripping surface and a shearing surface;
said shearing surface having a shape which conforms with the shape
of said knife edge,
whereby bone or tissue material to be sheared may initially be
gripped between said gripping surface and said knife edge with said
bone or tissue material then being sheared by movement of the first
cutting member relative to the second cutting member to bring the
knife edge and shearing surface into close shearing proximity.
5. The surgical tool of claim 4 wherein
the outer end of said first cutting member comprises a cutting tip
releasably secured thereto;
said cutting tip having a passage aligned with said passage in said
first cutting member, and
said cutting tip having an outer end which defines said knife
edge,
whereby said cutting tip may be replaced when said knife edge
becomes dulled.
6. The cutting tool of claim 5 including
a frictional surface within said passage in said cutting tip,
and
means to align said frictional surface in the passage of said
cutting tip with said frictional surface in the passage in said
first cutting member.
7. The surgical cutting tool of claim 1 including
power operated means to cause relative movement of said first and
second cutting members.
8. A replaceable cutting tip for a surgical tool comprising
a cutting tip body having an elongated configuration;
a longitudinal bore in said body;
said body having a forward end and a rearward end;
said forward end defining a knife edge;
means within said bore adapted to engage and disengage material
therewithin on movement of said body in a second direction and
first direction, respectively, and
means to releasably secure said cutting tip with said rearward end
in engagement with a surgical instrument.
9. The replaceable cutting tip of claim 8
wherein said means adapted to engage and disengage material within
said bore is a frictional surface, and
said frictional surface is a serrated surface directionally biased
to exert a frictional force on material within said bore on
movement of said cutting tip body in said second direction.
10. The replaceable cutting tip of claim 8
including a wall on said body;
a generally conical forward exterior surface on said body, and
said wall being progressively reduced in thickness in the direction
of said knife edge,
whereby said wall and forward exterior surface act as a wedge in
exerting a breaking force on material being cut by contact with
said knife edge with the cut being progressively enlarged through
contact with said forward exterior surface.
11. The replaceable cutting tip of claim 8 including
means to uniformly fix the rotational position of said body with
respect to a surgical instrument in engagement with the rearward
end of said cutting tip.
12. The replaceable cutting tip of claim 9 including
means to uniformly fix the location of said frictional surface with
respect to a surgical instrument in engagement with the rearward
end of said cutting tip.
13. The replaceable cutting tip of claim 8 wherein said knife edge
is circular.
Description
BACKGROUND OF THE INVENTION
A family of surgical instruments have been developed to perform
various gripping, holding, cutting, chipping or perforating
operations on bone and tissue. The operation situs is frequently
located in a relatively inaccessible place and, thus, the surgical
instruments may have varying shapes to accommodate their usuage in
a particular location. Further, to provide considerable force in
performing a particular operation procedure, the surgical
instrument may include a power source with control means to provide
increased force during the operating procedure with delicate
control of the surgical instrument. A surgical instrument with such
a power source is described in the United States Patent to Bent,
U.S. Pat. No. 3,752,161, dated Aug. 14, 1973, which is incorporated
herein by reference.
In previous surgical instruments of the type generally referred to
as forceps or rongeurs, cutting has generally been accomplished
through movement of a cutting member against an anvil. During use
of the instrument, the bone or tissue at the operation situs is
held between the cutting member and avil with the anvil and cutting
member then undergoing relative movement to bring the sharpened
edge of the cutting member into contact with the anvil. In this
type of surgical instrument, the cutting member may become dulled
from repeated contact with the anvil. This, in turn, may require
replacement of the cutting member by disassembling the surgical
instrument to replace the cutting member or to remove the cutting
member for sharpening.
In the use of a surgical instrument for operations performed at a
relatively inaccessible operation situs, the instrument may include
a recess which receives cut material that is removed by the
surgical procedure. Depending upon the extent of the operation and
the amount of bone or tissue which is surgically removed, the cut
material received in the recess may constitute a number of bites
with each bite resulting from one cutting movement of the
instrument.
In an extensive operation, the number of bites may exceed the
capacity of the recess for storage of surgically removed material.
In this event, it may be necessary to withdraw the surgical
instrument from the operation situs to discharge stored material
from the recess before proceeding with the operation. If the
operation is performed in an area where there is considerable
bleeding, the time lost in withdrawing the surgical instrument from
the operation situs may make the operation considerably more
difficult. For example, when the surgical instrument is withdrawn
from the operation situs, the flow of blood during the time
required for removal of bites from the recess may make it necessary
to remove blood from the operation situs before proceeding with the
operation.
A further complication of withdrawing the surgical instrument from
the operation situs is that time may be lost in cleaning the
instrument before proceeding with the operation. At the beginning
of the operation, the instrument will be in a clean condition,
e.g., by autoclaving. To clean the instrument, it is necessary to
remove the bites of material from the rongeur under sterile
conditions. This involves the expenditure of additional time which
would lengthen the operation.
It is advantageous to both the surgeon and patient if a surgical
operation can be performed in the shortest possible time. The shock
of the operation on the patient's system is related to the length
of the operation since this determines the extent of anesthesia,
the extent of supporting personnel to monitor the patient's vital
functions, and the time required in recovery before the regaining
of consciousness. Also, if the operation is performed in a shorter
period of time, difficulties in keeping the operation situs clear
will be reduced.
In view of the aforementioned problems, it would be desirable to
have a surgical instrument which would have less tendency to become
dulled during repeated usage. Also, it would be desirable to have a
surgical instrument in which dulling of the cutting member would
not require disassembly of the instrument to replace the cutting
member.
In addition, it would be desirable to have a surgical instrument
with means for storing bites removed by the surgical procedure in
which the surgical instrument would not have to be withdrawn from
the operation situs during the operation to remove bites from the
storage recess. This would permit more rapid performance of the
operation with less time expended in keeping the surgical field
clear, less shock to the patient, and less danger of infection.
SUMMARY OF THE INVENTION
As a solution to the aforementioned problems, the present invention
provides a surgical instrument having a first cutting member with a
passage therein. A second cutting member is slidably received
within the passage with a recess provided in the second cutting
member. A storage recess formed by the recess in said second
cutting member and said passage includes an inlet opening and a
discharge opening with the first and second cutting members having
a configuration which provides cooperative shearing action between
the cutting members during relative movement of the members in a
first direction.
During relative movement of the cutting members in the first
direction, sheared material removed at the operation situs is
deposited in the storage recess through the inlet opening. Means
are also provided to cause movement of the sheared material within
the recess toward the discharge opening during relative movement of
the cutting members in a second direction. The relative movement of
the cutting members in the first and second directions may result
from a power source such as a motor as illustrated in the Bent
patent or the relative movement of the cutting members may result
from movement of gripping members which may be moved manually by
the surgeon to transmit relative movement to the cutting
members.
In the present surgical instrument, the discharge opening is spaced
from the inlet opening to the storage recess. Thus, sheared
material within the storage recess is ejected through the discharge
opening at a point which is displaced from the operation situs such
that the discharge of sheared material does not interfere with the
operation.
The cooperative shearing action between the first and second
cutting members in the present surgical instrument reduces dulling
of the cutting members so that the surgical instrument can be used
for a longer time period before sharpening or replacement of the
cutting members. Also, the cooperative shearing action between the
first and second cutting members produces a cleaner cut so that
less difficulty may be involved in removing bites of cut material
from the operation situs.
During usage, the second cutting member may be slidably received
within the passage within the first cutting member. Thus, the first
cutting member serves to support the second cutting member and to
maintain the second cutting member in a desired position for
cooperation with the first cutting member. As bites of material are
removed at the operation situs, the bites are deposited within a
storage recess through an inlet opening, with movement of the first
and second cutting members in a second direction causing movement
of the bites toward a discharge opening that is displaced from the
inlet opening. Sheared material which is ejected through the
discharge opening is, thus, discharged at a point that is removed
from the operation situs.
If the operation is minor, the capacity of the storage recess may
be sufficient to retain the surgically removed bites without
ejection of sheared material from the discharge opening. However,
if the operation is more extensive and the number of bites exceeds
the capacity of the recess, the bites may be ejected through the
discharge opening without interference with the field of operation
at the operation situs. Thus, the surgeon will not be required to
withdraw the surgical instrument from the situs of the operation to
remove bites from the storage recess. The surgeon will, therefore,
be able to complete the operation in a shorter time which is a
convenience to the surgeon and also reduces the shock to the
patient's system that would result from a longer operation.
In the present surgical cutting instrument, the recess in the
second cutting member may include a smooth bottom slide surface
which cooperates with a frictional surface within the passage. The
frictional surface within the passage may be positioned to engage
sheared material supported on the smooth surface and to move the
sheared material along the smooth surface during relative movement
of the first and second cutting members in said second
direction.
The frictional surface provided within the passage is a serrated
surface directionally biased to engage sheared material within the
recess during relative movement of the cutting members in the
second direction and to disengage the sheared material within the
recess during relative movement of the cutting members in the first
direction. In this manner, the sheared material may be moved in a
stepwise manner along the smooth bottom surface from the inlet
opening to the discharge opening through engagement of the
directionally biased frictional surface with the material during
each relative movement of the cutting members in the second
direction.
In the present surgical instrument, the first cutting member may be
movable while the second cutting member is fixed. The first cutting
member may have a generally elongated construction, an outer end
defining a knife edge, and the passage in the first cutting member
positioned in a generally axial direction with respect to the first
cutting member. The second cutting member may have a generally
elongated construction with an outer support surface conforming to
the surface of the passage to slidably support the first cutting
member while the second cutting member may include an outer end
defining an inwardly facing gripping surface and a peripheral
shearing surface which conforms with the shape of the knife edge.
Bone or tissue may, thus, be gripped between the gripping surface
and the knife edge with the gripped material then being sheared
through movement of the first cutting member relative to the second
cutting member to bring the knife edge and peripheral shearing
surface into close shearing proximity.
In addition to providing an improved surgical instrument, as
described above, the present invention also provides a replaceable
cutting tip which may be used with a surgical instrument. Through
use of the replaceable cutting tip, the surgical instrument may be
more easily maintained without having to disassemble the instrument
to replace or sharpen its cutting members.
The replaceable cutting tip may include a cutting tip body having
an elongated generally cylindrical configuration with a
longitudinal bore defined within the body. The cutting tip body
includes a forward end and a rearward end with the forward end
defining a knife edge. Additionally, means may be provided to
engage sheared material within the bore of the replaceable cutting
tip during movement of the cutting tip body in a second direction
and to disengage sheared material within the bore during movement
of the cutting tip body in a first direction. Means may also be
provided to position the replaceable cutting tip with its rearward
end in engagement with a surgical instrument and with the means to
engage and disengage cut or sheared material within the bore of the
cutting tip being fixed in a desired position with respect to the
surgical instrument.
The means to engage and disengage sheared material within the bore
of the cutting tip body may include a serrated frictional surface
with the frictional surface being directionally biased to exert an
engaging force on sheared material within the bore of the cutting
tip on movement of the cutting tip body in said second
direction.
Preferably, the replaceable cutting tip includes a wall having a
generally conical exterior surface and with the wall being
progressively reduced in thickness in proceeding toward the knife
edge at the forward end of the cutting tip. The wall may, thus, act
as a wedge in exerting transverse force on material which has been
cut by contact with the knife edge, with the cut being
progressively enlarged through contact with the exterior surface of
the cutting tip.
BRIEF DESCRIPTION OF THE DRAWINGS
To further illustrate the invention, reference is made to the
accompanying drawings which illustrate a preferred embodiment of
the invention, and in which:
FIG. 1 is a side elevational view, partially in section, of a
surgical cutting instrument with bone or tissue extending into a
gap between first and second cutting members which undergo relative
movement in shearing bites of material from the bone or tissue;
FIG. 1A is a sectional view taken along line 1A--1A of FIG. 1 which
illustrates the second cutting member slidably received within a
passage in the first cutting member with a storage recess for
receipt of bites of sheared material which are conveyed to a
discharge opening that is removed from the operation situs;
FIG. 2 is an enlarged vertical cross-sectional view of the
instrument of FIG. 1 in which the first and second cutting members
have undergone relative movement in a first direction to remove a
bite of bone or tissue with the bite being deposited into the
storage recess
FIG. 3 is a sectional view taken along line 3--3 of FIG. 2
demonstrating the manner in which the outer surface of the second
cutting member engages a passage within the first cutting member to
slidably support the first cutting member while permitting relative
movement between the first and second cutting members;
FIG. 4 is a sectional view taken along the line 4--4 of FIG. 2
illustrating the manner of supporting the first cutting member
through contact between the passage in the first cutting member
with the exterior surface of the second cutting member;
FIG. 5 is an enlarged vertical cross-sectional view of the forward
end of the surgical instrument in which serrated frictional
surfaces are provided within a bore in a replaceable cutting tip
and within the passage in the first cutting member, which surfaces
are directionally biased to exert an engaging force on sheared
material in the storage recess during relative movement of the
cutting members to move the sheared material in the direction of a
discharge opening from the recess, and
FIG. 5A is a perspective view illustrating a means for fixing the
position of the replaceable cutting tip shown in FIG. 5 with
respect to a surgical instrument.
DETAILED DESCRIPTION
A surgical cutting instrument 2, as illustrated in FIG. 1, may
include a first cutting member 4 having a generally elongated
configuration with a longitudinal passage 6 within the first
cutting member. A second cutting member 8 having an exterior
surface 9 is positioned within the passage 6 with the exterior
surface 9 contacting the surface of the passage to provide slidable
support for the first cutting member 4.
A storage recess 10 is defined in the passage 6 by second cutting
member 8 with the recess having an inlet opening 12 and a discharge
opening 14. A replaceable cutting tip 16 may be positioned on the
first cutting member 4 with the replaceable tip defining a knife
edge 18 at its forward end. The second cutting member 8 may include
a transversely positioned gripping shoe 20 positioned at its
forward end with the gripping shoe including a lateral or
peripheral edge surface 22 and a transversely positioned gripping
surface 23.
As illustrated in FIG. 1, tissue or bone 24 which is to be removed
at the operation situs, may be positioned between the knife edge 18
and the transversely positioned gripping surface 23. Thus, during
relative movement of the first and second cutting members 4 and 8
in a manner to be described, a shearing force may be exerted on the
material 24 through the cooperative action of the shoe 20 and the
knife edge 18.
A fluid motor designated 26 may be used in providing relative
movement of the first and second cutting members 4 and 8. The fluid
motor 26 may, for example, take the form of the fluid motor
described in U.S. Pat. No. 3,752,161 to increase the cutting or
breaking force which is applied in a surgical operation while
retaining delicate control by the surgeon. However, the present
surgical instrument 2 may be actuated in any suitable manner or by
hand and, thus, the reference to fluid motor 26 is merely to
illustrate one means of actuating the surgical instrument.
The fluid motor 26 may include a trigger 28 and a grip 29 with
actuation of the trigger controlling the movement of a piston 30
within a cylinder 32 to transmit movement to the first cutting
member 4. The piston 30 is shown in FIG. 1 in a retracted position
under the influence of a biasing spring 34.
A support hub 36 is positioned about the exterior surface of the
first cutting member 4 with the support hub being fixedly held by a
collar 38 in threaded engagement with a body 39 for hydraulic motor
26. One end of the biasing spring 34 is retained within a recess 40
formed in the hub 36 with the recess terminating at a ledge 42
which engages the spring. The other end of the spring 34 engages
the piston 30 such that the biasing force of the spring tends to
move the piston to the right from its position shown in FIG. 1.
The second cutting member 8 may be supported with respect to the
hub 36 by any suitable means such as screws 44 and 45. As will be
described, the construction of the surgical instrument 2 permits
the support of the first cutting member 4 by the second cutting
member 8 while permitting relative movement between the two cutting
members.
Turning to FIG. 1A, which is a sectional view taken along line
1A--1A of FIG. 1, the passage 6 within first cutting member 4
surrounds the second cutting member 8 whose outer surface 9 is in
contact with the surface of the passage. The recess 10 within
passage 6 formed by the second cutting member 8 leads to the
laterally directed discharge opening 14. Thus, sheared material
within the recess 10 may be transmitted to the discharge opening 14
where it is ejected at a point that is removed from the operation
situs.
FIG. 2 is an enlarged vertical cross-sectional view of the cutting
members 4 and 8 after relative movement of the cutting members in a
first direction to shear off a bite 46 from bone or tissue 24 at
the situs of the operation. To facilitate the cutting action, the
replaceable cutting tip 16 may include a conical outer surface 47
which tapers inwardly toward the knife edge 18. This provides the
replaceable cutting tip 16 with a wall 49 whose thickness is
progressively increased in thickness in a direction away from the
knife edge 18. In cutting a bite 46 from the bone or tissue
material 24, the material may be cut initially through contact with
knife edge 18 with the cut then being progressively opened through
a wedging action by contact of the material 24 with the conical
surface 47. The wedging action produced by the conical surface 47
provides a transverse breaking force to the material 24 which
assists the severing of hard material such as bone or bony
tissue.
Preferably, the knife edge 18 is of a circular shape with the
lateral edge surface 22 of the gripping shoe 20 having a
corresponding circular shape. With knife edge 18 having a circular
shape, cutting is provided at any point around the knife edge that
is brought into shearing proximity with the lateral edge surface
22. Thus, it is not necessary that the knife edge 18 be aligned in
any particular manner with the material 24 to be cut as would be
the case if the knife edge had a shape where the cutting effect of
the knife edge would be altered depending upon its position with
respect to the material being cut.
As shown in FIG. 2, the knife edge 18 and lateral edge surface 22
are brought into close shearing proximity during cutting of a bite
46 from the material 24. When in close shearing proximity, the
knife edge 18 slides over the lateral edge surface 22. This
provides a cooperative shearing action between the knife edge 18
and lateral edge surface 22 in which the knife edge is not forced
against a rigidly positioned anvil surface which would produce more
rapid dulling of the knife edge. The movement of the knife edge 18
and the lateral edge surface 22 in cutting the bite 46 also
provides shearing coaction between the knife edge and lateral edge
surface which cuts more effectively than the action provided by
movement of a knife edge surface against a rigid anvil.
Additionally, the sliding movement of the knife edge 18 over the
lateral edge surface 22, shown in FIG. 2, forces the bite 46 into
the recess 10. As the bite 46 is moved into the recess 10, a
serrated directionally biased frictional surface 51 therein engages
the bite on movement of the first cutting member 4 in the direction
of discharge opening 14. This moves the bite 46 along a smooth
slide surface 48 toward the discharge opening 14.
As shown, the discharge opening 14 is displaced from inlet 12 (see
FIG. 1). Thus, when sheared material is ejected from the recess 10
through the discharge opening 14, its point of ejection is removed
from the operation situs. The ejection of sheared material through
the discharge opening 14 does not, therefore, interfere with the
operation. This is of considerable importance since it permits the
performance of the operation in a shorter time period which is of
advantage to the surgeon and is also of considerable advantage to
the patient.
During relative movement of the cutting members 4 and 8 with the
knife edge 18 and the lateral edge surface 22 being moved apart,
the bites 46 are transported through contact with a frictional
surface 51 along the slide surface 48 toward the discharge 14. Upon
reaching the discharge 14, the bites 46 engage an ejection surface
50. The ejection surface 50 is angled to provide a transverse
ejecting force to bites 46 as they contact the ejection surface.
The bites 46 are, thus, ejected through the discharge opening 14.
The rearward end of the replaceable cutting tip 16 may, as
indicated, be connected to the first cutting member through a
threaded connection 52.
Moving to the right in FIG. 2, the passage 6 within first cutting
member 4 leads to an enlarged passage 54 while the outer surface 9
of second cutting member 8 leads to an enlarged surface 56
positioned slidably within the enlarged passage. As will be
described, the second cutting member 8 may be fixedly held with the
first cutting member 4 being moved relative to the second cutting
member. During movement of the first cutting member 4, the first
cutting member may be slidably supported through contact of the
passage 6 with surface 9 and contact of the enlarged passage 54
with enlarged surface 56.
Movement of the first cutting member 4 is illustrated by arrow A in
which knife edge 18 undergoes movement toward the lateral edge
surface 22 to sever a bite 46 from the bone or tissue 24. During
movement of first cutting member 4 in the direction of the arrow A,
a drive end 58 formed integrally with the first cutting member is
moved to its solid line position by a force which overcomes the
biasing force of spring 34. Such movement may, for example, be
provided by movement of a piston, such as piston 30 illustrated in
FIG. 1. On removing the driving force from drive end 58, the action
of biasing spring 34 then returns the drive end to its phantom line
position 58'. During this movement, the drive end 58 and the first
cutting member 4 undergo movement in a direction opposite to that
indicated by arrow A, and the knife edge 18 is moved away from the
lateral edge surface 22.
As stated, the second cutting member 8 may be held in a fixed
position by screws 44 and 45 with the outer surfaces 9 and 56 of
the second cutting member slidably supporting the first cutting
member 4. The screws 44 and 45 threadedly engage apertures 60 and
62 in the second cutting member 8 with the screw fixedly held by
the hub 36 which has a flange 64 that is engaged by the collar 38
(see FIG. 1). Screw 44 extends through a side opening 66 in the hub
36 while screw 45 extends through a side opening 68. The head of
the screw 45 may be retained within a recess 70 such that the head
does not interfere with positioning of the collar 38 about the hub
36.
A saddle-shaped recess 72 is provided within the body of first
cutting member 4 and a saddle-shaped support spacer 74 is
positioned within the recess. The saddle-shaped support spacer 74
has the same configuration as recess 72; however, the spacer has a
length which is less than that of the recess. This permits relative
movement between spacer 74 and the first cutting member 4 with the
degree of relative movement determined by the distance between the
ends of recess 72 and the ends of the spacer.
The screws 44 and 45, in addition to passing through apertures 66
and 68 of hub 36, also pass through apertures 78 and 80 of the
spacer 74. This fixes the position of the spacer 74. The spacer 74
terminates at a pair of upper surfaces 76 shown in phantom line
drawing which are in contact with corresponding surfaces on the
first cutting member 4.
FIG. 3, which is a sectional view taken along line 3--3 of FIG. 2,
illustrates the manner in which the first cutting member 4 is
slidably supported by the second cutting member 8. As illustrated,
the position of second cutting member 8 may be fixed with a
plurality of screws, such as screw 44 which threadably engages
aperture 60 in the second cutting member 8. The saddle-shaped
support spacer 74 is also fixedly positioned with respect to hub 36
while the first cutting member 4 is slidably supported through
contact with second cutting member 8 and the support spacer 74.
Relative movement is, thus, permitted with the first cutting member
4 being free to slide in a longitudinal direction within the limits
permitted by the length of the recess 72 with respect to the length
of the support spacer 74.
FIG. 4, which is a sectional view along line 4--4 of FIG. 2,
illustrates further the manner in which first cutting member 4 is
slidably supported by the second cutting member 8. As illustrated,
the first cutting member 4 has been moved forwardly to bring an end
surface 82 or recess 72 into close proximity with one end 84 of the
spacer 74. At the same time, the other end 86 of recess 72 is moved
away from the spacer 74. The knife edge 18 is, thus, advanced
toward the gripping shoe 20 while first cutting member 4 is
slidably supported by the second cutting member 8. This movement is
designated by arrow A which is the same designation used in FIG. 2
to illustrate this movement of the first cutting member 4.
After completion of the cutting operation, the first cutting member
4 is moved in the direction of arrow B. During this movement, the
surface 82 of recess 72 is moved away from the end 84 of spacer 74.
During this movement, the surface 86 may be moved through the
distance designated C to bring the surface 86 into close proximity
with an end 88 of spacer 74.
FIG. 5 is an enlarged vertical sectional view, similar to FIG. 2,
illustrating the first cutting member 4 and second cutting member 8
with a plurality of bites 46 supported on slide surface 48. During
movement of the knife edge 18 toward gripping shoe 20, the
frictionally biased surface 51 disengages the bites 46 within the
storage recess 10. However, after severing a new bite 46 and
depositing it in recess 10, the frictionally biased surface 51
engages the bites 46 to move the bites toward the discharge opening
14 as the knife edge 18 is moved away from shoe 20.
If desired, the passage 6 in first cutting member 4 may also
include a frictionally biased surface 90 positioned in aligned
relation with frictional surface 51. Thus, during movement of the
first cutting member 4, both the surfaces 51 and 90 function to
engage bites 46 on movement of the first cutting member in one
direction and to disengage the bites on movement of the first
cutting member in a second direction.
In the use of two frictional surfaces 51 and 90, it is desirable
that the replaceable cutting tip 16 be precisely positioned on the
first cutting member 4 so that the two frictional surfaces are
properly aligned. To accomplish this result, a connection 92
between cutting tip 16 and first cutting member 4 may be employed
which fixes the rotational position of the cutting tip with respect
to the first cutting member.
A suitable connection for fixing the rotational position of cutting
tip 16 with respect to first cutting member 4 is illustrated in
FIG. 5A. The cutting tip 16 may include a male socket member 94
which fits in a corresponding female socket member in the first
cutting member 4. A shoulder 95 on the tip 16 then engages an end
surface 97 on the first cutting member 4 with a pin 96 on the tip
in engagement with an L-shaped slot 98 in the first cutting member.
After inserting the pin 96 into slot 98, the replaceable cutting
tip 16 may be rotated with respect to the first cutting member 4 to
bring the pin into contact with a slot end surface 100. This, then,
fixes the rotational position of the replaceable cutting tip 16
with respect to the first cutting member 4 which, in turn, aligns
the frictionally biased surfaces 51 and 90 (FIG. 5) within the
cutting tip and the first cutting member.
* * * * *