U.S. patent number 3,753,621 [Application Number 05/134,694] was granted by the patent office on 1973-08-21 for concrete-working machine with walking vibrators.
Invention is credited to Charles Harry Dale.
United States Patent |
3,753,621 |
Dale |
August 21, 1973 |
CONCRETE-WORKING MACHINE WITH WALKING VIBRATORS
Abstract
Concrete-working machine component with concrete-spreading
auger, vertically adjustable strike-off plate, forwardly
projecting, vertically oscillatable arms bearing depending
vibrators which reciprocate into and out of the concrete, and crank
or cam drives for said arms.
Inventors: |
Dale; Charles Harry (Rock
Island, IL) |
Family
ID: |
22464529 |
Appl.
No.: |
05/134,694 |
Filed: |
April 16, 1971 |
Current U.S.
Class: |
404/116 |
Current CPC
Class: |
B28B
1/0935 (20130101) |
Current International
Class: |
B28B
1/093 (20060101); B28B 1/08 (20060101); E01c
019/38 () |
Field of
Search: |
;425/120,424,456
;94/45,46,48 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Byers, Jr.; Nile C.
Claims
The invention is hereby claimed as follows:
1. A machine adapted for imparting vibrations to poured concrete at
spaced intervals comprising frame means, at least one arm
projecting forwardly of said frame means, pivot means pivotally
supporting said arm on said frame means for substantially vertical,
oscillating movement of said arm, power driven means connected to
said arm at a point on said arm forwardly of said pivot means and
providing said oscillating movement by the forward portion of said
arm, said power driven means including means to change the amount
of vertical oscillation of the forward ends of said arm, an
elongated power-driven vibrator having its upper portion mounted on
the forward portion of said arm and depending vertically therefrom,
the lower end of said vibrator adapted to be moved up and down into
and out of poured concrete by the oscillating movement of said
forward portion of said arm.
2. A machine as claimed in claim 1, said machine having at least
two of said arms contiguous to each other, and the respective
elongated vibrators depending vertically therefrom being
substantially aligned one behind the other.
3. A machine as claimed in claim 1, wherein said pivot means
comprises substantially vertical, oscillatable arm means pivotally
supported on said frame means and pivotally connected to said
arm.
4. A machine as claimed in claim 3, said power driven means
including a crank having a crank rod connected to said arm
forwardly of said oscillatable arm means.
5. A machine as claimed in claim 4, and means rigidly attaching
said crank rod to said arm whereby rotation of said crank imparts
via its crank rod positive oscillating motion to said oscillatable
arm means.
6. A machine as claimed in claim 5 wherein the crank arm of said
crank orbits in the lower half of its rotation cycle in a rearward
direction.
7. A machine as claimed in claim 3, said power driven means
including a rotatable cam, and a cam follower for said cam mounted
on said arm.
8. A machine as claimed in claim 1, and a rotatable auger extending
transversely of said frame means behind said vibrator.
9. A machine as claimed in claim 8, a vertical strike-off plate
extending transversely of said frame means and positioned behind
said auger, and means mounting said plate on said frame means in
vertically adjustable relation of said plate to said frame
means.
10. A machine as claimed in claim 1, said vibrator having its upper
portion pivotally supported on the forward portion of said arm by
pivot means allowing forward and rearward pivotal movement of said
vibrator.
11. A machine as claimed in claim 10, said vibrator comprising an
elongated vibrator member driven by a motor on the upper end
thereof.
12. A machine adapted for imparting vibrations to poured concrete
at spaced intervals comprising frame means, at least one arm
projecting forwardly of said frame means, means pivotally
supporting said arm on said frame means, power driven means
providing substantially vertical, oscillating movement by the
forward portion of said arm, a power-driven vibrator depending from
the forward portion of said arm and adapted to be moved up and down
in poured concrete by the oscillating movement of said forward
portion of said arm, said first-mentioned means comprising
substantially vertical, oscillatable arm means pivotally supported
on said frame means and pivotally connected to said arm, said power
driven means including a rotatable cam and a cam follower for said
cam mounted on said arm, and stop means coacting with said
oscillatable arm means to limit pivotal movement of said arm
means.
13. A machine adapted for imparting vibrations to poured concrete
at spaced intervals comprising frame means, at least one arm
projecting forwardly of said frame means, means pivotally
supporting said arm on said frame means, power driven means
providing substantially vertical, oscillating movement by the
forward portion of said arm, a power-driven vibrator depending from
the forward portion of said arm and adapted to be moved up and down
in poured concrete by the oscillating movement of said forward
portion of said arm, said first-mentioned means comprising
substantially vertical, oscillatable arm means pivotally supported
on said frame means and pivotally connected to said arm, said power
driven means including a rotatable cam and a cam follower for said
cam mounted on said arm, and means mounting said follower on said
arm and providing a plurality of positions for mounting said
follower at longitudinally spaced intervals along said arm.
14. A machine as claimed in claim 13, and means for mounting said
oscillatable arm means on said frame means in a plurality of
positions spaced in similar longitudinal intervals to said
longitudinally spaced intervals along said arm.
Description
INTRODUCTION
The concrete-working machine component of the present invention is
particularly adapted for use with machines for spreading, vibrating
and finishing of prestressed concrete slabs in elongated T-molds or
double T-molds. The molded concrete products are substantially
rectangular slabs having one or two longitudinal ribs projecting
from a face thereof. The ribs contain a plurality of cables under
tension, which are laid in the rib-forming cavities of the bottom
wall of the single T-or double T-mold under tension prior to the
pouring of concrete into the mold. The slab portion of the concrete
may contain wire mesh, reinforcing rods or other concrete
reinforcing means.
One of the problems encountered heretofore in the use of concrete
spreading, compacting and finishing machines used on single T- or
double T-molding forms lies in the area of attainment of suitable
vibration of the poured concrete in the longitudinal, rib-forming
cavities of such molds. One technique used to attain such vibration
is having one or two men stand on the machine who manually dip into
and out of the poured concrete, concrete vibrators as the machine
moves longitudinally along the form.
The subject invention concerns a concrete-working machine component
adapted to be used in association with a rear machine component for
compacting or working, e.g., through tamping, and finishing the
slab-forming portion of the concrete in such single T- or double
T-molds. The machine component has at least one and preferably a
plurality of motor driven concrete vibrators which dip into and out
of the concrete to a depth sufficient to vibrate the poured
concrete in the rib-forming longitudinal cavities in the bottom
wall of the single T- or double T-mold. These vibrators attain
their reciprocal motion into and out of the concrete by the
mounting thereof on the forward portion of one or more arms which
are vertically oscillatably driven through a power drive. The power
drive mechanism preferably embodies a crank or cam for each arm to
impart the oscillating motion.
Concrete paving machines known heretofore have utilized vibrators
adapted to dip into and out of concrete as a machine goes forwardly
along the surface to be paved. For example, Mall U.S. Pat. No.
2,248,103 illustrates ganged, manually operated rocker arms
respectively having a vibrator pivotally hung from the forwardly
projecting portion of the arm. Mall U.S. Pat. No. 2,223,734 shows a
similar type of paving machine with the vibrators being
gang-mounted on a manually oscillatable frame. Other U.S. Pats.
disclosing vibrators or vibrating compacters adapted to reciprocate
or to be moved relative to the poured concrete include U.S. Pat.
Nos. 2,255,344, 2,261,659, 2,292,733, 2,332,687, 2,651,979,
3,123,872 and 3,224,064.
THE INVENTION HEREIN
Briefly, the subject invention relates to concrete-working machines
particularly adapted to impart vibrations to poured concrete at
longitudinally spaced intervals as the machine goes forwardly along
a concrete form. The machine component with which the subject
invention is principally concerned embodies frame means, at least
one arm projecting forwardly of the frame means, and means
pivotally supporting the arm on the frame means. Power driven means
are operatively associated with each forwardly projecting arm to
provide substantially vertical, oscillating movement to the forward
portion of the arm. This oscillating movement provides vertical
movement into and out of concrete poured ahead of the machine by
one or more vibrators depending from the forward portion of the
respective arms. Preferably, the vibrators are dipped into the mold
cavities at 3-6 inch intervals.
The machine component of the subject invention preferably also
embodies a rotatable auger extending transversely of the frame
means behind the vibrator(s). This auger preferably is rotatably
driven by drive means (not shown) permitting it to be rotated in
either direction to attain satisfactory spreading of the concrete
between the side walls of the form. A vertical, strike-off plate
positioned contiguous to and behind the auger extends transversely
of the frame means. Its lower edge strikes off poured concrete
accumulated against the front face of the strike-off plate and
provides a substantially flat upper surface to the poured concrete
in the mold. In the machine component of the subject invention, the
strike-off plate is mounted on the frame means in vertically
adjustable relation to the frame means to provide the desired depth
of strike off by said lower edge.
The preferred embodiment of the invention has, for each rib-forming
cavity of the T-mold, at least two arms contiguous to each other,
each arm being oscillatably driven by the power drive means,
preferably about 180.degree. out of phase. The vibrators on the
respective arms are substantially aligned one behind the other.
With the aforesaid 180.degree. out of phase drive, one vibrator is
dipping into the poured concrete in the mold while the other is
being withdrawn.
The pivotal support of respective arms preferably is attained
through substantially vertical, oscillatable arm means pivotally
supported on the frame means and pivotally connected to the
rearward portion of each respective arm. The oscillatable arm means
permit each forwardly projecting arm and the respective vibrator
depending therefrom to move in substantial reciprocating action
within predetermined limits, the advantages of which are
hereinafter described.
The power drive means for the respective arms preferably embody a
crank or cam for imparting the vertical oscillating motion to the
forward portion of each arm. With a crank drive, the rod connecting
the crank arm to the forwardly projecting arm preferably is rigidly
connected to the forwardly projecting arm. Such rigid connection
imparts to the substantially vertical oscillatable arm means a
positive oscillating motion determined by the orbital movement of
the crank arm. The crank itself preferably is oriented in terms of
its direction of orbit so that it orbits through the lower half of
its rotation cycle in a rearward direction. This relationship
imparts a rearward movement to the forwardly projecting arms and
vibrators depending therefrom in a direction opposite to the
direction of forward movement of the machine while the vibrators
are dipped into the poured concrete. Such rearward movement in part
or in whole, depending upon the velocity of forward movement of the
machine and rate of rotation of the crank, cancels out the effect
of forward movement of the machine while the vibrators are dipped
into the concrete, whereby the vibrators remain in substantially
vertical position while they are in the concrete and are not
pivoted rearwardly as a result of said forward motion to any
significant extent.
In another preferred form of the invention, the power driven means
for the forwardly projecting arms include a rotatable cam with the
cam follower for the cam mounted on the forwardly projecting arm.
In this embodiment, the substantially vertical, oscillatable arm
means has associated therewith and coacting therewith stop means to
limit pivotal movement of the arm means. The follower preferably is
mounted on its respective arm by mounting means providing a
plurality of positions for mounting the follower at longitudinally
spaced intervals along the arm. Such plurality of positions permits
the follower to be laid closer to or further away from the pivotal
support of the rearward portion of the forwardly projecting arm and
thereby adjust the range of vertical movement of the forward
portion of such arm and the vibrator depending therefrom. Where the
pivotal support for the rear portion of the forwardly projecting
arm is the aforesaid substantially vertical, oscillatable arm
means, the base of the latter is mounted on the frame means in any
one of a plurality of positions spaced in similar, longitudinal
intervals to the longitudinally spaced intervals for mounting the
cam follower on the forwardly projecting arm.
DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are illustrated in the
drawings wherein:
FIG. 1 is a perspective view of a first embodiment of the aforesaid
concrete-working machine component and its relationship to a double
T concrete mold, shown in fragment;
FIG. 2 is a side elevation illustrating the crank drive and
vertical arm pivotal support for the forwardly projecting, vibrator
supporting, vertically oscillatable arms;
FIG. 3 is a fragmentary, exploded view of the vertically adjustable
means for mounting the strike-off plate on the frame means of the
machine component;
FIG. 4 is a side elevation, partly in cross section, similar to
FIG. 2 wherein the forwardly projecting arm is vertically
oscillated by a cam drive;
FIG. 5 is a side elevation of an alternate form of cam useful in
the embodiment in FIG. 4; and
FIG. 6 is a diagrammatic view of the relative motion imparted to
the forwardly projecting arms and the vibrators depending therefrom
at 90.degree. intervals in the rotation of the crank drive in the
embodiment of FIGS. 1 and 2.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Referring to the drawings, the concrete-working machine component
10 constitutes the front section of an overall concrete-working
machine. The rear section is not illustrated inasmuch as it
corresponds substantially to the rear section disclosed in my U.S.
Pat. No. 3,377,933, which is incorporated herein by reference. The
rear section is used for propelling the machine component 10
forwardly along the concrete mold, e.g., by the cable and winch
drive illustrated and described in my aforesaid patent.
The metal frame means 11 for the machine component 10 is composed
of side channels 12 and 13; heavy wall, tubular, cross frame
members 14 and 15 which are rigidly attached, e.g., by welding, to
the inner faces of the side channels 12 and 13 by connector plates
16 and 17; and a platform 18 rigidly attached to and extending
across the tops of the tubular frame members 14 and 15.
The front portions of the side channels 12 and 13, respectively,
have yokes 20 and 21 in which are rotatably journalled flanged
wheels 22 and 23. These wheels ride on rails 25 and 26, which in
turn are fixedly attached to the flanges 27 and 28 of the side
walls 29 and 30 of the elongated, concrete mold 31. The bottom wall
32 of the mold contains, in the case of double T molds, a pair of
parallel, longitudinally extending, elongated cavities 33, one of
which is illustrated and the other of which is disposed directly
under the vibrators 60a and 60b. In the case of molding of
prestressed concrete slabs with one or two ribs, the cavities 33
have longitudinally disposed therein a plurality of tensioned
cables, usually lying in a vertical plane about midway between the
side walls of the cavities 33. Wire mesh or other reinforcing means
may be laid in the mold over the bottom wall 32 to reinforce the
slab-forming portion of the molded concrete product.
The concrete-working machine component 10 has at the rear portions
of the side channels 12 and 13 upper coupling members 35 and lower
coupling members 36 by which the machine component 10 is coupled to
the aforesaid rear section described in my aforesaid patent.
Referring to said patent, the rear section in the overall machine
herein contemplated preferably embodies at least a cable and winch
forward propulsion mechanism and power drive therefor; the tamper
bar and its drive mechanism, the power units and control unit, a
flat or crowned pan beneath the frame of the rear section, which
pan need not embody the crown adjustable mechanism nor the curb
forming sheet which is illustrated and described in my aforesaid
patent, and optionally the reciprocable, rear finishing screed.
The front machine component 10 of the subject invention has an
auger 40 extending across the machine between the side channels 11
and 12, which auger is rotatably journalled on the side channels
and is rotatably driven and controlled from the rear section of the
machine is described and illustrated for the auger in my aforesaid
patent. A vertically adjustable strike-off plate 41 extends between
the side channels 12 and 13 immediately behind the auger. The
reversible drive for the auger is used by the machine operator to
maintain an accumulation of wet concrete across the entire length
of the strike-off plate 41, the lower edge 42 of which (FIG. 3)
strikes off and levels the upper surface of the wet concrete. The
rear section of the machine may also embody a strike-off plate set
at the same or a slightly lower level than the strike-off plate 41.
See, for example, the strike-off plate in my aforesaid patent.
The strike-off plate 41 is mounted on the frame means 11 in
vertical, adjustable relationship thereto by a pair of
hydraulically operated, vertical adjustment means 43 and 44. The
components of the vertical adjustment means 43 and 44 are
illustrated in FIG. 3. The front, tubular cross frame member 15
and/or respective mounting plates 16 and 17 have fixedly secured
thereto, e.g., by welding, a metal L-channel 46. A U-frame 47 is
rigidly attached to the front face of the L-channel 46. A wider,
inverted U-frame 48 fits telescopically over the U-frame 47 as
illustrated in FIG. 1. A hydraulic cylinder 49 with a piston rod 50
is positioned inside the frames 47 and 48. A yoke 51 on the end of
the piston rod 50 is coupled by a bolt or pin (not illustrated) to
the cross legs 52 of the inverted U-frame 48 with the bolt or pin
extending through apertures 53 in the cross legs and apertures in
the yoke 51. The inverted U-frame 48 is rigidly attached to the
rear face of the strike-off plate 41.
The yoke 54 of the hydraulic cylinder is coupled in a similar
manner by bolts or pins (not illustrated) extending through
apertures 56 in the cross legs of the U-frame 47. The respective
hydraulic cylinders 49 of the strike-off plate's vertical
adjustment means 43 and 44 are coupled by conventional hydraulic
fluid lines to the hydraulic control and pressure system provided
on the rear section of the machine.
The machine as illustrated has four concrete vibrators 60a, 60b,
60c and 60d which dip into and out of the wet concrete poured in
the concrete mold ahead of the machine. These vibrators have an
essentially vertical reciprocating motion to a height sufficient to
lift them completely out of the wet concrete and to a depth
sufficient that the respective lower ends of the vibrators
penetrate into the rib-forming cavities 33 in the bottom wall 32 of
the mold.
Each vibrator 60a, 60b, 60c and 60d is of conventional construction
and is driven by respective electric motors 61a, 61b, 61c and 61d.
The upper portions of the vibrators are respectively pivotally hung
in yokes 62a, 62b, 62c and 62d by pins 63 which allow the vibrators
to pivot in a front to rear and rear to front pivotal motion. The
yokes 62a, 62b, 62c and 62d and the vibrators hung therein have an
oscillating motion in respective vertical planes imparted thereto
by the drive imparted to the rear portions of the respective
forwardly projecting arms 64a, 64b, 64c and 64d.
The illustrated cam or crank drives for the forwardly projecting
arms 64a-d impart a substantially vertical, oscillating movement to
the vibrator-supporting, forward portion of each arm. The
respective vibrators 60a-d appear, when the machine is in motion,
to have a walking-like action as they dip into and rise out of the
wet concrete poured in the mold.
With the preferred vibrator arrangement illustrated in FIG. 1,
there are two pairs of contiguous arms 64a, 64b and 64c, 64d, in
this case in side-by-side relationship. Thus, two vibrators are
dipping into and out of the concrete for each of the mold cavities
33 with the vibrator pairs 60a, 60b and 60c, 60d being
substantially aligned one behind the other. The pivotal support 63
of the vibrators in the respective yokes 62a-62d allow them to
pivot enough to pass wire mesh and/or cables embedded in the poured
concrete in the event that the latter should be struck by the
vibrator.
The preferred means for pivotally supporting the respective arms
64a-d is illustrated in FIGS. 1, 2 and 4. This means comprises a
pair of substantially vertical, oscillatable arms 66 pivotally
connected by hinge structure 67 to a base plate 68. The latter is
connected by bolts 69 to the platform 18.
The upper ends of the arms 66 are pivotally connected by hinge
structures 70 to a base plate 71 in turn bolted to the lower side
of the respective arm 64a-d. In FIGS. 2 and 4, the arm 64a was
selected for illustrative purposes.
In the embodiment of FIGS. 1 and 2, the power driven means which
provides the substantially vertical, oscillating movement to the
forward portion of the respective arm 64a-d is a crank drive 72a,
72b, 72c or 72d. The crank structure in each case embodies a
rotatably driven disc 73 having an orbiting crank pin or arm 74
projecting from a face of the disc 73. A bearing-containing head 75
is rotatably journalled on the pin or arm 74. The head 75 is bolted
to the upwardly extending connector rod 76 at the lower end of the
latter. The upper end of the connector rod 76 is rigidly connected
by a mounting plate 77 and bolts 78 to the lower side of the arm
64. If desired, spacer plates 79 may be interposed between the arm
64a and the mounting plate 77 to vary the vertically reciprocable
path imparted to the respective vibrators 60a-d. Similarly, if
desired, spacer plates 79 may be interposed between the base plate
71 and the arm 64a for the same purpose.
The rigid connection between the arm 64a and the connector rod 76
provides a positive oscillating motion to the respective arm means
65a-65d. As the crank pin or arm 74 orbits through the upper half
of its rotation circle, the arm means 65a-d are thrust forwardly
relative to the machine frame. As the crank pin orbits through the
lower half of its circle, the arm means 65a-d are thrust
rearwardly, again relative to the frame of the machine.
The aforesaid relative motion is illustrated diagrammatically in
FIG. 6 wherein the arrows 80 designate the forward motion of the
machine along the mold. The arrows 81 designate the relative
forward movement of the arm 64a and the vibrator 60a depending
therefrom attained through positive oscillation of the arm means
65a. The arrows 82 designate the relative rearward motion imparted
to the arm 64a and its vibrator 60a. The latter relative motion
occurs when the vibrator has approximately or actually penetrated
the upper surface 83 of the poured wet concrete. Thus, while the
respective vibrator is in the concrete mass, the relative rearward
motion designated by arrows 82 in part or in total, depending upon
the linear velocity of the machine and the rate of rotation of the
cranks, offsets the forward direction of travel of the machine
designated by the arrows 80. This offsetting relationship is
advantageous in that the pivotally hung vibrators remain in
substantially vertical position while their lower,
vibration-imparting ends are in the concrete.
If desired, the crank disc 73 may have one or more alternate crank
pins 84 projecting from the face thereof at a different radius than
the axis of rotation of the disc 73. These alternate crank pin(s)
provide means for changing the amount of oscillating movement of
the arm means 65a-d and also the oscillating movement of the
forwardly projecting arms 64a-d and thus can be used to vary the
intervals at which the respective vibrators 60a-d dip into and out
of the concrete as well as the amount of vertical movement of the
respective vibrators.
The cranks 72a-d are power driven by drive shafts 85 and 86
rotatably journalled in bearings 91, in turn mounted on the
platform 18. The drive shaft 85 is driven by a chain and sprocket
coupling 87, one sprocket of which is driven through reduction gear
box 88 by a variable speed belt-pulley drive driven by an electric
motor 89. Electric cable connections for the motor (not
illustrated) are coupled to an electric power source, e.g., the
generator and the motor control unit shown on the rear section of
the machine described and illustrated in my U.S. Pat. No.
3,377,933. The shaft 86 is driven off the shaft 85 at a 1:1 drive
ratio by th chain and sprocket coupling 90.
In the embodiment of FIG. 4, a cam drive is used in lieu of the
crank drive for each arm 64a-d, the arm 64a again being used for
illustrative purposes. Where applicable, like numerals designate
like parts previously described. The cam drive does not provide the
rigid connection with the arm 64a which is provided by the
illustrated crank drive. Hence, the base plate 68 is mounted on a
mounting plate 95 by the bolt 69 in any pair of a plurality of
front to rear, aligned, tapped holes 96 in the plate 95, the
purpose for which will be later described.
Additionally the base plate 68 has rigidly mounted on its front and
rear edges the vertical plates 97 and 98 in which are threadably
mounted respective horizontal bolts 99 and 100. These bolts are
aligned with the arm 66 and serve as stops which limit the
oscillating motion of the arm 66.
The cam 101 and its cam follower 102 impart oscillating movement to
the arm 64a and also impart a forward oscillating movement to the
arm 66. When the follower 102 is riding on the circular curved
portion 107, the vibrators are in the down, concrete penetrating
position. As the cam rotates in the arrow direction, its
lift-imparting curve 108 oscillates arm 64a upwardly while at the
same time imparting a forward thrust against the cam follower 102.
This thrust causes the arms 66 to oscillate forwardly until they
contact the bolts 100. The relatively straight cam surface 109
allows the vibrators to drop relatively rapidly into the wet poured
concrete while at the same time permitting the arm 66 to be
oscillated rearwardly as a result of forward motion of the machine
relative to the concrete in which the lower end of the vibrator is
buried. The arms 66 are thus oscillated rearwardly by thrusts
imparted through the vibrator and its arm until the arms 66 strike
bolts 99.
The cam 101 of FIG. 4 has an indentation 105 which extends the
circular curve 107 and thus keeps the respective vibrator in the
lower position for a longer period of time.
If desired, however, the cam may be made without the indentation
105 in accordance with the shape of the cam 106 shown in FIG. 5
wherein the circular curve 107 and the lift-imparting curve 108
merge smoothly into each other.
The amount of oscillating movement imparted to the arm 64a by the
cam drive can be changed by moving the oscillatable arms 66 closer
to or further away from the cam 101 or 106 by changing the position
of the bolts 69 into another pair of tapped holes 96 in the
mounting plate 95. The cam follower 102 is shifted a corresponding
amount by the mounting thereof between a pair of plates 103, each
containing a horizontal row of apertures 104 spaced at intervals
corresponding substantially to the spacing of tapped holes 96. By
way of illustration, the cam follower 102 may be a cylinder
rotatably journalled on a removable bolt or pin in turn supported
in one of the apertures 104 of each of the plates 103.
It is thought that the invention and its numerous attendant
advantages will be fully understood from the foregoing description,
and it is obvious that numerous changes may be made in the form,
construction and arrangement of the several parts without departing
from the spirit or scope of the invention, or sacrificing any of
its attendant advantages, the forms herein disclosed being
preferred embodiments for the purpose of illustrating the
invention.
* * * * *