CA1121712A - Tire changing machine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A tire-changing machine includes a framework supporting a wheel rim receiving platform adapted to receive and secure a wheel rim thereon. A bead breaker mechanism includes a bead breaker shoe, and 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 therethrough in which the shoe support arm is slidably engaged, 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 direction parallel to the support column causes a friction force between the lock member and the shoe support arm sufficient to arrest motion of the shoe support arm in the channel.

Description

"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 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~
~ - 3 -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 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 _ .

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 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.

,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.

- 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 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.

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 %
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 ~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~

Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In combination with a tire-changing machine of the type wherein a framework supports a wheel rim receiving platform adapted to receive and secure a wheel rim thereon, wherein a bead breaker mechanism includes a bead breaker shoe, and wherein 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, the improve-ment comprising a bead breaker shoe support arm having the shoe fastened to one end thereof, a bead breaker column lock member having a channel therethrough in which said shoe support arm is slidably engaged, so that said support arm is ad-justable in lateral position to bring the shoe to over-lie the tire bead, and a bead breaker support column providing a mount for said solumn lock member and being pivotally connected to the bead breaker drive lever at one end, so that a force component applied to the shoe in a direction parallel to said support column causes a friction force between said lock member and said shoe support arm sufficient to arrest motion of said shoe support arm in said channel.

2. The combination of claim 1 together with means for pivotally connecting said bead breaker support column to the framework at a point intermediate the ends of said column, said pivotal connection between said bead breaker support column and the drive lever being positioned so that inital drive lever motion moves said connection downardly and outwardly, whereby the shoe moves downwardly inwardly toward the wheel rim drop centre.