Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
"J /3 ~
This inven-tion relates to tire-changing machines
and more particularly to such machlnes as are provided with a
stand for supporting the tire to be changed in a horizontal
position with upper and lower bead breakers which separate
the tire bead from the wheel rim.
The prior art, a-~ least insofar as the patent
literature is concerned is voluminous. Certain patents are
directed to upper bead breaker mechanisms, other patents to
the lower bead breaker mechanism, and further patents to
mechanisms for driving a central post and still further
patents to combinations of these and other features.
The most relevant prior art known to the inventor
is as follows:
U.S. PATENT NO. ISSVED _VENTOR
3,847,198 November 12, 1974 Brosene, Jr.
3,807,477 April 30, 1974 Curtis
3,742,999 July 3, 1973 Myers, Jr.
3,358,730 December 19, 1967 Mandelko
3,255,800 June 14, 1966 Stran~
3,212,5S2 Oc-tober 19, 1965 Foster
3,165,142 January 12, 1965 Tabordon
3,158,190 November 24, 1965 Foster
3,064,718 November 24r 1962 Brosene, Jr.
Elements of these structures have been and are still
employed in commercially available machines, for example the
double lower bead breaker shoe, of U.S. 3,158,190, the
pneumatically powered machine with the single lever co-action
between the upper and lower bead breakers and the central drive
post of U.S. 3,212,552, the hook-shaped upper bead breaker of
U.S. 3,255,800, and -the various mechanisms of U.S. 3,847,198,
U.S. 3,807,477 and U.S. 3,742,999.
However, the development of alternative wheel rims
such as magnesium or alloy wheels together with the wider
'J~ ~
~ ranges of sizes of wheel rims has macle the use o~ -these machines
increasingly difficult and has resulted in unsatisfactory
performance.
E'or example the standard wheel structure usually
employs a fl~nge on the wheel rim of between 3/8" and 1/2" as
compared to the wider flange of 3/4" on alloy wheels. With many
conventional -tire changers of either the single or double lower
bead breaker type -the locus followed by the leading edge of the
lower bead breaker shoe is usually an arc oE a circle. While
the wheel-receiving table top may accommodate diferent sizes of
wheel rims such a path does not permit accommoda-tion of wheel
rim flanges of differing widths. Thus while such a lower bead
breaker may effectively break a bead on a standard wheel rim it
will frequently hit the wheel rim of an alloy wheel with either
the first or second lower bead breaking shoe. Since the tire
obscures the view of -the operator, considerable damage can be
done to the alloy or magnesium wheels. The operator may not
detect the wrong engagemen-t and the rim may be fractured or
dented.
A similar problem arises wi-th upper bead breakers of
the prior art. These may take the form shown in U.S. 3,255,800
to Strang previously referred to, or they may have the form
shown in U.S. 3,807,477. The two types referred to are entirely
different in structure and action and give different
difficulties.
With the second type the column which supports the
upper bead breaker is pivoted to move about a single pivot point
and again the bead breaker arm moves -through an arc. In this
type of structure the "nose" of the bead breaker arm engages the
bead or the sidewall of the tire. The arcuate motion of the
-- 2
bead brea~er tencls to pull the bead breaker nose outwards and
downwards and the engac3ement between the bead breaker "nose" and
the sidewall is not too ~ecure. This frequently results in the
"nose" sliding off or a downward and outward pull being exerted
on the wall. This action is not always effective in breaking
the tire bead at the rim.
In the first mentioned s-tructu-re a nose is provided to
engage the inner surface of the wheel rim. The rotational pull
on the bead-hreaker column is -translated into an outward
horizontal force against the wheel rim and a downward force
against the tire sidewall or bead. The horizontal force may be
as great as 25,000 lbs. This force frequently damages the wheel
rims particularly if they are of alloy.
The "nose" of this first-mentioned upper bead breaker
is also provided with a secondary arm which is spring--loaded to
maintain it in engagement with the tire bead and follow the tire
bead into the wheel well. However, the mechanism does not so
Eunction in practice through out the travel of -the bead breaker
column. Frequen-tly, after the upper bead breaker column has
completed part of the travel the bead will not break because the
vertical force is not sufficient to break the bead. The
operator then drops the upper bead breaker column relative to
the turning lever and repeats the bead-breaking procedure so
that the bead can be broken. The upper breaker mechanism which
has just been discussed also has a further difficulty in that
the adjustments available to the operator are limited by the
provision of limited pivot points at the bottom of the vertical
column and relatively fixed relationship of the bead breaker
shoe to the "nose" which is itself pivoted at one point. ~o
meaningful lateral adjustment i9 available without changing the
force exerted on the bead to break it~
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Machines of the prior art have three furtherprincipal shortcomings, their complexity and cost, and a
further operational problem. The second of these arises
because the centre post driving mechanisms usually drive
through a limited range and since they usually rely on a
simple hydraulic power source are provided with a spring
return to reverse the motion. However, in operation when the
operator inserts the
tire tool in the bead and over the centre post and
rotates the tire tool to pry the bead from off the wheel
rim, because the bead is normally broken in the bead-
breaking operation over a limited range, the tire tool
frequently binds between an unbroken section of rim
and bead. The result is that the tool is stuck and
the spring return does not provide sufficient power
to release the tire tool so that another attempt can
be made.
With these difficulties in mind it is the
object of the presen~ invention to provide an improved
tire-changing machine which is economical to build,
easy to operate and which may be operated with a min-
imum of dama~e to wheel rirns.
In accordance with the present invention a
tire-changing machine is provided of the type wherein
a framework supports a wheel rim receiving pla-t-
form adapted to receive and secure a wheel rim thereon,
wherein a bead breaker mechanism includes a bead
breaker shoe. The shoe is operatively connected to
a bead breaker drive lever so that the bead of a
tire mounted on the rim may be engaged by the shoe and
broken away from the rim. A bead breaker shoe support
arm has the shoe fastened to one end thereof, and
a bead breaker column lock member has a channel there-
through in which the shoe support arm is slidably
enga~ed, so that the support arm is adjustable in
lateral position to bring the shoe to overlie the
tire bead. A bead breaker support column provides a
mount for the column lock member and is pivotally
connected to the bead breaker drive lever at one end~
so that a force component applied to the shoe in a
~-4-
direction parallel to the support column causes a ~riction
force between the lock member and the shoe support arm
sufficient to arrest motion of the shoe support arm in
the channel.
-5 The foregoillg objects and features of -the
present invention will be more fully appreciated ~rom
the following description and drawings in which a
specific embodiment is described by wa~v of example
and in which:
Fig. 1 is-a general perspective view of ~
tire changer in accordance with the present invention;
Fig. 2 is a general perspective view with the
cover removed and partially broken away wi-th conven-
tional structural elements omitted for the purposes
of illustrating more clearly the spatial relation-
ship between those parts which constitute the inven-
tion;
Fig. 3 is a diagrammatic sectional view taken
along line 3~3 of Fig. l and shows a tire changer in
accordance with the present inven-tion with a tire on
a wheel rim mounted thereon prior to removal of the
tire;
Fig. ~ is a general perspective view of an
upper bead breaker in accordance with the presen-t in-
~5 vention;
Fig. 5 is a section taken along line 5-5
of Fig. 4;
Fig. 6 is a side view of the upper bead breaker
mechanism illustrated in Fig. 4 and serves to illustrate
the lateral adjustment capability of the pres~' inven-
tion;
-4a-
r~
Fig. 7 is an enlarged side view of an upper
bead breaker mechanism in accordance with -the present
invention illustrating the relationship of the upper
bead breaker shoe, a kire, wheel rim and the upper part
of the tire-changing during the initial part of the
travel of the upper bead breaker shoe;
Fig. 8 is a partial plan view paxtly in
section illustrating the relakionship between the
central shaft and the rack and pinion gear for driving
the shaft;
Fig. 9 is a side view partly in section
illustrating the travel and motion of the upper bead
breaker mechanism relative to the tire, wheel rim
and its actuating lever;
~5-
Fiy. 10 is a side view partly in section
illustrating the completiorl of the bead-breakiny action and
the relationship of the various parts of the machine at this
point of opera-tion.
Fiy. 11 is an enlaryed diagrammatic sectional view
of a lower bead shoe in relation to a tire and serves to
illustrate i-ts method of operation.
It will be understood that struc-tural details such
as bushinys, bearings, screws, nuts and bolts and the like
are provided where s-tandard engineering practice would
'require. Such details have been omi-tted from this
description because their illustration and presence would
detract from the essential structural details and hinder
rather than help in the understanding of the drawings and
description.
ReEerriny now -to the drawinys, in Fig. 1 a
tire-changing machine in accordance with the present
invention is indicated yenerally at 10. As shown it
comprises a casing or cover 11 surrounding a frame upon which
is provided a deck 14 with a wheel rim receiving platform 12.
The w'heel rim pla-tform 12 has yenerally frustro-conical shape
with inwardly slopiny surfaces 27 and 2~ on the ascending
plane. It has been found that in such models of this present
machine as are provided with inflating air tubes as shown at
13 in,Fig. 3 that the conical confiyuration in combination
with the adjacent undersurface of the tire wall lead to a
more efficient means of injectiny air under pressure in-to the
tire upon infla-tion than o-ther,forms which are circular in
yeometry. In deck 14 there are two slots one extending
transversely as at 15 adjacent platform 12 and one 16 on the
-- 6 --
7~l~
remote side o~ platform 12 fro~n slot 15 and extending along
the longitudinal axis of the deck 14.
From slot 15 a lower bead breaker shoe 20 projects
when normally at rest and from slot 16 an upper bead breaker
support arm 21 ex-tends.
From the upper surface of platform l2 a rotatable
shaft 23 extends vertically and on one side thereof, through
slot 24 a pin 25 extends. Pin 25 is adapted to engage a bol-t
hole in a wheel rim to help secure the wheel rim against
relative rotational movement thereto.
A frame 26 has a generally rec-tangular form
fabricated from square tubing and is provided with a pair of
side plates 30 and 31. Deck 14 is mounted on the frame. The
plates 30 and 31 support and are spaced apart by transversely
15 extending rods such as 32, 33, 34, 35 and 36. These rods
also serve as pivotal mounts for air/hydraulic cylinders 37
and 38; the upper bead breaker levers 39 and 40; the lower
bead breaker guide arms 41 and 42; and the upper bead breaker
guide arms 43 and 44, respectively.
The air/hydraulic cylinders 37 and 38 are
connected, in reverse respectively, to an air supply by air
hoses 45 and 46 and -to each other by an oil hose 47.
The air supply is in turn controlled by a valve
operated by foot pedal 50 in a conventional manner.
Cylinders 37 and 38 are each pivotally mounted
through collars 49 and 51 on rods 32 and 33, respectively,
and the:ir respective pistons 52 and 53 are also pivotally
connected to rods 54 and 55. Rod 54 is itself pivotally
mounted on the lower bead breaker guide arms 41 and 42.
The upper bead breaker levers 3g and 40 are a pair
of parallel plates pivotally mounted on rod 34 as mentioned
previously. These plates each are irregular in form and are
provided with openings such as at 56 through which rod 35,
which is the pivotal mounting for the lower bead breaker
guide arms 41 and 42, passes and which supports these guide
arms 41 and 42 ou-tward of plates 3g and 40.
Rod 55 at -the left hand end of pla-tes 39 and 40
spaces them apart and rods 57 and 58 also serve this
purpose. Rod 58 is pivotally mounted and is also pivotally
connec-ted adjacen-t to the lower end of -the upper bead breaker
column 21.
Rod 57 also piv~otally supports a lever arm 59 at
one end. The remaining end of lever arm 59 i9 pivotally
connected at 60 to a rack 61 which engages a pinion gear 62
on the lower end of the shaft 23. The necessary bearings,
not shown, will, of course, be provided. The rack 61 is
supported by a rack guide 63 and this assembly is supported
by two ver-tical brackets 64 and 65 welded across the frame to
provide further reinforcement. For clarity, the frame is not
- shown in Fig. 2.
The bolt hole engaging pin 25 is also mounted on
this subassembly (Figure 3) so that it may move towards and
away from shaft 23 in slot 24. ~owever, i-t is provided with
a collar 67 and a spring 68 so that -the collar 67 is biased
in-to engagement with the underside of the table top wall~
This arrangement facilitates engagement between a wheel bolt
hole and the pin.
The lower bead breaker shoe 20 as mentioned
previously is pivotally mounted on rod 54. Shoe 28 has an
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_ .
arcuate leading edge 72 for engaging the tire bead. This
leading edge 72 is on an inner por-tion inclined a-t an angle
to an outer lower portion. The inner portion is indicated at
70 and the outer portion a-t 71. From the outer portion the
pivotal connection is made through a pair of spaced apart
depending brackets. The attitude of the leading edge 72 is
determined by a pair of adjustable screws such as 73 which
engage a plate 74 mounted on arms 41 and 42. Arms 41 and 42
ensure that the lower shoe follows a predetermined path to
attack the tire bead at a proper angle. The adjustmen-t b~
means of the screws provides a further adjustment.
The upper bead breaking mechanism comprises an
upper bead breaking shoe 80 with a leading edge 81. Again
the leading edge 81 is arcuate in plan view for engaging the
upper tire bead. Leading edge 81 extends along the boundary
of an inner downwardly inclined tongue portion 82 which
depends from a vertical portion 83 of the upper shoe. The
vertical portion 83 is hingedly connected by a pin 8~ which
extends through an inverted U-shaped portion 85 of the upper
shoe and an upper bead breaker support arm 86. The upper
bead breaker support arm 86 has an angular cut at the end
thereof as at 87 and a spring 88 is mounted between the upper
surface of the arm 86 and the lower surface of the inverted
U-shaped portion of the shoe.
Support arm 86 passes through an arm guide member
89. The arm guide member has a pin 90 fixed bet~een the side
walls of the guide members. The fit between the support arm
86 and the channel through the arm guide member is a loose
sliding fit to permit the upper bead breaking shoe to be
moved laterally with the support arm. However, when an
:. _ 9 _
, upwardly directed force component is applied -to the upper
- bead breaker shoe 80 as at F (Flgure 5), the support arm 86
is caused to move upwardly at the end on which the s'hoe is
moun-ted and the upper surface of -the arm is brought into
sharp engagement with the upper wall of the guide member 89
and the lower surface of the arm is brought into sharp
contact with -the upper surface of the pin 90. This provides
a binding action between the suppor-t arrn 86 and the surfaces
at which sharp con-tac-t occurs to provide a fric-tional lock
which prevents the support arm 86 from moving laterally in
the channel through the arm guide member.
The arm guide member 89 has a horizontally
projecting square tube member 91 attached thereto which has
an opening 91a through the upper surface and an opening 91b
through the lower surface t'hereof. The openings 91a and 91b
may be circular openings and are slig'htly larger in diameter
than the diameter of -the upper bead breaker column 21 so that
the column passes therethrough wi-th a sliding fit.
When a vertically upward force F is direc-ted
against the upper bead breaker shoe 80 the square tube member
91 is seen to rotate in a clockwise direc-tion about an axis
disposed radially with respect to the column 21 as seen in
Figure 5. In such an instance the left side of the upper
opening 91a and the right side of the lower opening 91b as
shown come into sharp engagement with the outer surface of
the upper bead breaker column 21. Since the areas at the
edges of the openings in con-tact with the column are
relatively small due to the relatively thin upper and lower
wal]s of the square tube member 91, a high pressure i5
generated between the contacting edges of the openings and
-- 10 --
the column as the couple imposed by the upwardly directed
force on the shoe is counterac-ted. As a consequence the
edges of the openings in the square tube member 91 literally
"bite" into the surface of the upper bead breaker column
effecting a fric-tional locking engagement between the column
and -the square tube member. The upper bead breaker shoe 80
is thereby prevented from moving vertically on the bead
breaker column.
~t rest the engagemen-t between the bead breaker
column 21 and the square guide tube 91 also provides a
frictional lock therebe-tween as the weight of the shoe 80
tends to tilt the square tube member 91 in a counterclockwise
direction as seen in Figure 5. In such an instance the right
side of the upper opening 91a and the left side of the lower
lS opening 91b are brought in-to sharp contac-t with the column 21
to provide the "biting" action and corresponding vertical
locking func-tion as hereinbefore described for an upwardly
directed force on the upper bead breaking shoe. A pair of
handles such as 100 and 101 attached to the square tube
member 91 and the upper bead breaker support arm 86
- respec-tively provide easy adjustment of the upper bead
breaker assembly on the bead breaker column 21 without the
necessity for adjustment of any mechanical locks or screws.
By simply lifting the handle 100 when the upper bead breaking
assembly is at rest to thereby slightly rotate the assembly
in a clockwise direction as seen in Fiyure S the friction
lock between -the edges of the openings 91a and 91b and the
column 21 is broken. In this fashion the upper bead breaker
assemb]y may be adjusted in an infinite variety of positions
vertically on the upper bead breaker column 21.
-- 11 --
,2~7~2
Upper bead breaker column 21 is pivo-tally mounted
adjacent its lower end to t`he upper bead breaker levers 39
and 40 through rod 58 and intermediate its length by rod 96
to guide arms ~3 and ~ which are themselves pivotally
rnounted on the frame through rod 36.
It is to be noted that the pivotable connections -to
rods 96 and 36, as is eviden-t from Figure 3 are in
substantially the same horizontal plane. It is also to be
noted -that the pivot point of rod 58 is ini-tially, as shown
in Figure 3, above the pivo-t point of upper bead breaXer
levers 39 and 40. The upper bead breaker levers pivot about
the rod 3~ which is in a plane below that of the rod 58.
The significance of these relationships will be
more apparent from the description of the action and motion
of the upper bead breaker assembly which will be described
presentlyO It should be apprecia-ted -that the initial motion
oE the upper bead breaker shoe 80 will be inward and downward
into the wheel drop centre in con-trast to those upper bead
breaker mechanisms of the prior ar-t which are downward and
outward.
It will be apparent that the facility of adjusing
the upper bead breaker shoe and the engagement with the
column 21 permits the upper bead breaXer shoe assembly to
swing round to give clear access to the deck and wheel mount
platform 12.
In -the drawings a tire 200 mounted on a wheel rim
201 is placed on platform 12. Shaft 23 passes through the
hub hole in -the wheel rim and pin 25 passes -through a bolt
hole. A cone 102 threaded onto shaft 23 holds the wheel rim
30 201 down and pin 25 prevents relative rotation.
- 12 -
- r~he p1atform 12 will accommodate wheel rims from
10-inch diameter up to 17-1/2-inch diameter. The position of
the wheel rim on -the platforrn 12 will of course depend on its
diameter, the largest diameter wheel sits lowest down on
platform 12 while the smallest diameter wheel will sit higher
up the platform.
It will be understood -that the operator, depending
on the wheel rim flange si~e and the diameter of the wheel,
will have adjusted -the attitude of the leading edge 72 of the
lower bead breaking shoe 20 by adjus-ting screws 73 so as to
vary the distance be-tween the shoe 20 and the shoe support
plate 74. It will also be noted that the shoe support 74 is
considerably shorter than the bead breaking shoe 20 and has
no bead breaking function.
The opera-tor then adjusts the upper bead breakin~
shoe 80 so that the leading edge thereof, 81, is resting on
the -tire 200 adjacen-t the upper bead in the manner shown in
Fig- 3-
It will be apparen-t from the description of the
upper bead breaker shoe assembly that effecting proper
. engagement between the upper bead breaking shoe and the tire
bead is simple and easy. For a height adjustment, depending
on the wheel wid-th, the operator simply grips handle 100 and
tilts it clockwise from -the position shown in Figure 5, thus
releasing the frictlon lock between the square tube member 91
and the column 21, and moves the assembly vertically to the
required posi-tion on the column 21. The square tube member
may for facility be designated a column lock member. At the
selected posi-tion the operator merely releases -the handle 100
and again the column lock member 91 is frictionally engaged
- 13 -
with column 2l as hereinbefore described.
Simi.larly, -to adjust the upper bead breaker shoe
laterally the operator merely lifts handle 101 and moves the
upper bead breaker shoe suppor-t arm 86 horizontally. The
frictional engagement between the arm 86 and both the pin 90
and -the arm guide 89 is released by the lif-t applied to -the
handle 101 and when the shoe is in the selected lateral
position after movement and handle 101 is released there will
be no relative movemen-t between the tire 200, shoe 80 and
column 21. After the tire has been secured on the table 12
and the shoe positions adjusted the operator then operates
foot pedal 50 and actuates the air/hydraulic cylinders 37 and
38.
Initially the air supplied to cylinder 38 causes
piston rod 53 to extend and the oil above -the piston passes
into cylinder 37 and causes the air above the piston -to be
expelled and piston rod 52 to be extended. Because rods 52
and 53 are respectively pivotally connected to the lower bead
breaking shoe 20 and the upper bead breaker levers 39 and 40,
and their respec~ive cylinders are pivotally connected to
rods 32 and 33 the levers and shoes w.ill be caused to move to
assume the positions shown in Fig. 10.
As pis-ton rod 52 of cylinder 37 extends the lower
bead breaker shoe 20 is pivotally mounted on rod 54 and guide
arms 41 and 42 moves up and about the pivot provided by rod
35. Arms 41 and 42 cause shoe 20 and its leading edge 72 to
move through an arc initially. The arc of the l.eading edge
72 will of course vary depending upon the rela-tionship of the
shoe to its support 74. ~lowever, the lowes-t setting in this
relationship will ensure that a 3/8 inch rim is cleared at
the upper point of prospective engagement.
- 14 -
As the arms 41 and 42 move round and piston 52 isextended -the shoe 20 engages the sidewall not with its
leading edge 72 but so engages that the leading edge is free
to engage the lower tire bead. Since pivot 35 is below pivot
54, the locus of the lower bead breaker shoe will be inward
towards the wheel rim drop centre.
As the shoe 20 engages the tire sidewall it will
slowly move away from its support 74 and then the leading
edge moves in towards the bead. rrhe further -the -travel -the
more leading edge 72 of the lower bead breaker shoe can
follow the wheel rim wall.
This action is shown in Fig. 11 where the initial
starting position of the various components is shown in solid
outline and the final position is shown in dotted outline.
rrhe upper and lower bead breakers in the present machin~
operate on diame-trically opposed tire beads so that there is
additional resistance to assist in breaking the bead on the
side to which pressure is being applied.
- As piston 52 extends so simultaneously does piston
20 53. rrhis action causes pla-tes ox levers 39 and ~0 to rotate
about pivot 34. With this pivoting action the lower end of
column 21 through pivot 58 is caused to move outwardly at
first then inwardly and downwardly. This action is
illustrated in Fig. 9. At the same time guide arms 44 and 43
25 -through pivots 36 and g6 cause column 21 to rotate inward so
that the coaction of the guide means 43 and 44 and levers 39
and 40 is to cause the upper par-t of column 21 to move inward
and downward initially and to then continue downward and
inward subsequently. This action is illustrated in Figs. 7
and 9 where the initial starting position is illustrated in
- 15 -
%
solid outline and a subsequent position is shown in dotted
outline.
As mentioned in -the structural description, the
upper bead breaker shoe is pivotally mounted on the upper
bead breaker shoe support arm 86. As column 21 moves down
there is an ini-tial pivotal movement of shoe 80 about its
pivot 8~ and the leading edge 81 will be caused -to move in
towards the bead slightly against the resilience of spring
88. As the downward inward motion con-tinues -this pressure
engagement against the tire wall and the bead is main-tained
and the bead is broken.
At the breaking point the pressure on the shoe is
released and -the travel of the upper bead breaker column 21
need not be maintained.
lS At this poin-t -the upper bead breaker shoe may be
lifted up the column 21 and swung to the side. As upper bead
breaker arms 39 and 40 move down lever 59 through pivot 57 is
pulled down and rack 61 is pulled out towards -the right in
the drawings. The engagemen-t between rack 61 and pinion gear
62 causes shaft 23 to rotate.
In a manner similar to machines of the prior art
the operator then inserts a bead-breaking tool under -the tire
bead and over shaft 23. The foot pedal 50 is depressed and
shaft 23 rotated in the manner just described. If the tool
is stuck he then reverses -the mechanism by operation of the
foot pedal and the same power as was applied during the
- initial cycle is applied in reverse and the tool will be
freed wi-thout diEficulty or danger.
The tire remoun-tiny operation is accomplished in
the reverse manner, and in such models as are provided with
- 16 -
~IZ.~
inflatable air lines 13 surrounding the lower limits of *he
tire-receiving platform 12 -the conical form of the platform
makes for easier inflation guiding the air into the bead
rather than deflecting the air as is the problem with
arcuately formed tire-receiving platforms.
From the foregoing description i-t will be seen that
an improved tire-changing machine has been provided in which
the possibility of damage to magnesium and other forms of
alloy wheel rims has been minimised. At the same time it
will be noted that there is considerable facility in use.
The use of two power plants and the use of
air/hydraulic power uni-ts provides a smoothness of operation.
The air/hydaulic systems also are self-dampening so that the
irregularities and unevenness of forces which occur as a
result of the sudden absence of resistance when -the bead is
broken or there is a greater force required to break a bead
are more easily absorbed by this structure. The inward
travel of both upper and lower bead breaker shoes also gives
an efficiency not previously at-tained. The absence of a
necessity to compensate for outward forces on the wheel rims
grea-tly reduces -the damage on wheel rims and also leads to
more efficient bead breakage. The direct vertical force with
a minimal inward component does not break tire beads
efficiently. This coupled with the relief from pressure when
the upper bead is broken has permitted more efficient faster
tire changing.
I-t will be understood that the specific embodiments
disclosed may be varied and o-ther mechanisms may be
substituted for -those described without departing from the
scope of the claims appended~
- 17 -
