US3654736A

US3654736A - Blade-retention system for a blasting machine

Info

Publication number: US3654736A
Application number: US856079A
Authority: US
Inventors: John E De Groot
Original assignee: Benfur Engineering Co
Current assignee: Benfur Engineering Co
Priority date: 1969-09-08
Filing date: 1969-09-08
Publication date: 1972-04-11
Anticipated expiration: 1989-04-11

Abstract

A locking system for blasting machine blades is based upon locking members mounted in the spacers maintaining the relative position of axially spaced wheel discs receiving the blades in radial grooves. The blades extend radially beyond the periphery of the wheel discs, and have an offset engaging the peripheral surface to limit inward blade movement.

Description

[15] 3,654,736 5] Apr.1l, 1972 De Groot [54] BLADE-RETENTION SYSTEM FOR A BLASTING MACHINE [72] Inventor: John E. De Groot, Grand Rapids, Mich.

[73] Assignee: Benfur Engineering Company, Grand Rapids, Mich.

[22] Filed: Sept. 8, 1969 [21] Appl. No.: 856,079

[52] U.S.Cl ..51/9 [5 l Int. Cl. ..B24c 3/04 [58] Field of Search ..51/9

[56] References Cited UNITED STATES PATENTS 3,241,266 3/1966 Bowling ..51/9 3,383,804 5/1968 I-laider ..51/9

Primary Examiner-Lester M. Swingle Attorney-Glenn B. Morse [5 7] ABSTRACT A locking system for blasting machine blades is based upon locking members mounted in the spacers maintaining the relative position of axially spaced wheel discs receiving the blades in radial grooves. The blades extend radially beyond the periphery of the wheel discs, and have an offset engaging the peripheral surface to limit inward blade movement.

4 Claims, 12 Drawing Figures PATENTEDAPR 11 I972 3, 654. 736

sum 1 OF 2 I 7 INVENTO John E. DeGroo r Fig. 5 E

BLADE-RETENTION SYSTEM FOR A BLASTING MACHINE BACKGROUND OF THE INVENTION A blasting machine projects a stream of abrasive particles accelerated to high velocity by the action of a throwing wheel. This wheel has a general resemblance to a paddle wheel, and provision is made for the injection of particles of abrasive material in the central area of this wheel. Radially-arranged blades receive a flow of abrasive particles, and the rotation of the wheel generates the high velocity. The engagement of the abrasive particles with the blades produces extreme wear conditions, and the blades are normally manufactured from cast alloyed material of extreme hardness. These blades are frequently replaced, and are received within generally radial locating slots that extend to the outer periphery so that the blades can be slid into and out of the machine. The relatively high centrifugal forces involved require the provision of a reliable locking arrangement. Many of these have been devised, and are almost invariably based upon some sort of locking member interengaging a portion of the blade with at least one of the wheel discs. Set screws having threaded engagement with the wheel discs are common, as well as spring clip arrangements of the type shown in Barnes, U.S. Pat. No. 2,8l9,562. An arrangement involving a moveable locking member bridging across between the two wheel discs is shown in De Groat et al., U.S. Pat. No. 3,352,064.

In addition to locking the blades against the action of centrifugal force, it is also desirable to have some arrangement limiting the inward movement of the blade so that a new replacement blade can be slid into place with automatic positioning such that the locking system is in approximate alignment for engagement. If this is not provided, the radial slots in the wheels will permit the blade to slide inwardly into the central area of the wheel. This can be prevented, of course, by manually holding the blade in approximately the correct radial position while the locking system is interengaged. The requirement of this much manual manipulation is undesirable, and is preferably replaced by some positive stop arrangement.

The principal problem encountered in the continued effective functioning of a blade-positioning system is the effect of the stream of abrasive. Moving parts tend to become jammed as abrasive particles work their way into the spaces between the moving surfaces. Another requirement of an effective locking system is excessibility at the outer periphery of the throwing wheel. These wheels are normally confined within a housing, with a small access door being provided for the changing of blades. Since the blades are slid out and inserted radially, the presence of the locking system at the point of blade insertion is a distinct advantage.

SUMMARY OF THE INVENTION This invention provides a locking system transferring forces to the disc spacers, rather than directly to the discs themselves. The spacers are positioned close to the back of the blades (the opposite surface from that receiving the stream of abrasive), and a locking member mounted on the spacer is positioned to engage some sort of offset on the blade. The locking member may be in the form of an end portion on a cantilever spring, the opposite end being secured to the spacer. Locking can also be accomplished by a cam mounted on a rod arranged generally radially with respect to the wheel, the outer end of the rod being engageable with an actuating wrench. A further modification of the invention provides a locking action through a moveable plug mounted in the spacer, and engageable with a suitable recess in the blade. These arrangements all have the advantage of reducing the complexity of the wheel discs, and require no special access openings in the housing. Special provision is made in these modifications for minimizing the effect of abrasive particles on the working parts.

DESCRIPTION OF THE DRAWINGS In the drawings, FIG. 1 is a sectional elevation through a blasting machine in which one embodiment of the invention has been incorporated for retaining the blades in position.

FIG. 2 is a perspective view of one of the disc spacers of the assembly illustrated in FIG. 1.

FIG. 3 is a perspective view on an enlarged scale one of the blades shown in the FIG. 1 assembly.

FIG. 4 illustrates a modified form of the locking member from that shown in the FIG. 1 assembly.

FIG. 5 illustrates the form of locking member shown in the FIG. 1 assembly.

FIG. 6 is a sectional elevation on the plane 6-6 of FIG. 7 perpendicular to the axis of rotation of the machine shown in FIG. 1, illustrating the locking action in the FIG. 1 assembly.

FIG. 7 is a section on the plane 7-7 of FIG. 6.

FIG. 8 is a view on a plane similar to that of FIG. 6, but illustrating a modified form of the invention.

FIG. 9 illustrates a further modification of the invention, and is a sectional view taken on a plane transverse to the blades and parallel to the axis of rotation.

FIG. 10 is a view on the plane 10-10 of FIG. 9.

FIG. 11 illustrates a further modification of the invention, taken on a plane similar to that of FIG. 9.

FIG. 12 is a section on the plane 12ofFIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the illustrated blasting machine includes a throwing wheel generally indicated at 20 mounted on the shaft 21 for rotation within the bearing structure 22. The throwing wheel 20 includes the

discs

23 and 24 secured to the hub 25 by bolts as shown at 26 and 27. The disc 24 is the only one secured directly to the hub 25, with the

discs

23 and 24 being secured with respect to each other by spacers as shown at 28 and 29. These spacers are of a channel-shaped configuration as shown in FIG. 2, being secured by the bolts 30 to the discs 23 and by the bolts 31 to the disc 24. These bolts traverse the

flanges

32 and 33, leaving the back portion 34 to serve the function of spacing the

discs

23 and 24, and providing a base for the locking system provided by this invention. The remainder of the wheel structure shown in FIG. 1, including the abrasive inlet 35, the abrasive impeller 36, and the control cage 37 are standard construction.

In the locking system shown in FIG. I, the spacers are provided with a central opening 38 transversed by the cantilever leaf spring locking member 39. Blades are shown at 40 and 41 are received within the usual radial slots in the

discs

23 and 24, and are spaced evenly around the periphery of the wheel structure 20. These blades are each provided with shoulders as shown at 42 and 43 in FIG. 3, for engagement with the

peripheral surfaces

44 and 45 of the

wheel discs

23 and 24, respectively, to limit the inward movement of the blades, and minimize the diameter of the discs for a given requirement of blade surface. The inner extremity of the blade is beveled as shown at 46 in FIG. 3 for clearance with respect to the stream of abrasive induced by the adjacent blade at the relatively crowded space near the axis of rotation. This beveled surface is utilized by the present invention additionally for assisting in the placement of a spring-biased locking member.

Referring to FIG. 6, the initial insertion of the blade takes place with the bevel 46 entering the wheel at the opening of the slots. As the blade is moved to the right, as shown in FIG. 6, the surface 46 contacts the locking member 47, which is a portion of a cantilever leaf spring secured to the back 34 of the spacer 28 by the bolt 48. Continued movement of the blade 40 to the right will induce upward deflection of the locking member 39 to the point that the portion 47 will ride over the back surface 49 of the blade. The portion 47 will ultimately drop into the recess 50, and the blade will then be locked against the action of centrifugal force tending to move the blade back out to the left, as shown in FIG. 6. As the intensity of this force develops, the resilience of tee spring 39 will permit the portion 47 to become crowded between the righthand end of the recess 50 (as shown in FIG. 6) and the lefthand extremity of the opening 38 in the spacer.

The security of this arrangement can be increased by the use of the modified locking member shown in FIG. 4. The portion 51 of this modification is relatively wider than the opening 38 in the spacer, which is slightly in access of the width of the portion 52, secured to the spacer by a bolt such as the bolt 48 shown in FIG. 6. In the assembly of the unit shown in FIG. 4, the portion 52 is moved upward through the opening 38, and then rotated down into position where the bolt 48 can be secured. In such an arrangement, the radial extend of the opening 38 can be much less than that illustrated in FIG. 6, since only a sufficient gap is required to admit the portion 52, and permit rotation into the mounted position. The FIG. 4 lock requires clearance between the back of the blade and the spacer of at least the thickness of the portion 51.

In the modification shown in FIG. 8, the channel-shaped spacer 53 is provided with a hole in the back 54 slightly larger in diameter than the diameter of the wire of which the spring member 55 is formed. The locking action is provided by the end 56 which traverses the hole in the back 54, and enters an aligned recess in the blade 57. To increase the resilience of the spring, so that a heavier gage of wire may be used for greater locking strength, it is preferable to incorporate a coil 58 of one or two turns. This will increase the ability of the spring to accommodate upward deflection to a sufficient extent to withdraw the end 56 from the recess in the blade 57. The spring member is secured in position by the bolt 59 engaging a loop 60. To avoid tendency for tightening of the bolt 59 to swing the spring across the surface of the back 54, it is preferable to incorporate a shield 61 having a portion 62 engaging the outer end of the spacer 53 to prevent rotation of the shield as the head of the nut is turned.

Referring to FIGS. 9 and 10, the

wheel discs

63 and 64 are separated by the spacer block 65, which is secured in position by the

bolts

66 and 67. This spacer is mounted closely to the back of the blade 68, the position of which is determined by the conventional slots in the

discs

63 and 64. A hole in a substantially radial direction through the center of the spacer block 65 receives the rod 69 in rotatable relationship. The locking arm 70 is secured to the inner end of this rod, and swings to and from a position engaging an aligned recess in the blade 68. Actuation of the cam is accomplished by a suitable wrench engaging the squared end 71 of the rod 69, and it will be noted that this end is adjacent the outer periphery of the wheel where it will be exposed at the point where the blade is withdrawn and inserted. If desired, a compression spring 72 can be incorporated as shown in FIG. to establish increased resistance to rotation of the rod 69, or the opposite ends of the spring 72 can be secured, respectively, to the spacer 65 and the rod 69 to affect a torsional bias tending to maintain the cam 70 in engagement.

The modification illustrated in FIGS. 11 and 12 provides a locking action through the plug 73, which is slidably mounted in a suitable bore in the spacer block 74. This block maintains the spaced relationship of the

wheel discs

75 and 76, and is located adjacent the position of the back of the blade 77. The spacer is secured to the wheel discs by bolts as shown at 78 and 79. A hole 80 in a generally radial direction is open at the outer extremity, and intersects the hole in which the locking plug 73 is accommodated. Prior to the assembly of the plug 73 into the spacer block 74, the spring 81 and the ball 82 are inserted. The plug has a narrow waist 83 of a radius preferably somewhat greater than that of the ball 82, and receives the ball under the pressure of the spring 81 to maintain the relative position of the plug illustrated in FIG. 12. The head 84 of the plug may be engaged by the end of a screwdriver, with the comer 85 of the spacer functioning as a fulcrum, to raise the locking plug 73 a sufficient extent to withdraw it from the recess in the blade 77 in which the lower end of the plug is received for locking engagement. The conformation of the spacer block 74 and the orientation of the hole' 80, is such as to inhibit the inflow of abrasive particles during the operation of the machine. These particles have a direction of movement from right to left, as shown in FIG. 12, and the open outer extremity of the hole 80 will tend to provide a path of egress for any particles that find their way into such a position as to bind the motion of the locking plug.

I claim:

1. A system for locking the blades of a blasting machine, said machine having axially spaced discs separated by spacers and defining a throwing wheel normally mounted on a rotatable shaft, said discs having substantially radial grooves receiving the edges of said blades, wherein the improvement comprises:

locking means mounted on said spacers and engageable with said blades to prevent outward movement thereof, said spacers being provided with apertures disposed transversely with respect to an adjacent blade, and said locking means including a plug having a portion thereof transversing said aperture and slideably mounted with respect to said spacer, and having a head normally disposed on the opposite side of said spacer from said blade.

2. A system as defined in claim 1, including detent means mounted in said spacer and engageable with said plug to maintain the locking position thereof.

3. A system as defined in claim 2, wherein said detent means is mounted in a hole in said spacer open exclusively on the radially outermost face thereof, and intersecting a hole receiving said plug.

4. A throwing wheel for a blasting machine, said wheel having at least one disc disposed with a peripheral edge, said disc being secured to a hub member and provided with radial grooves, said wheel also having blades disposed with a portion of at least one edge thereof received in one of said grooves, said wheel also having locking means adapted to secure said blades against the action of centrifugal force, wherein the improvement comprises:

portions on said blades extending radially beyond said peripheral edge of said disc, said blade portions having an offset engageable with said peripheral edge to limit inward movement of said blades.

Patent No. 3,654,736 Dated Agril H, 1972 Inventor(s) John E. DeGroof It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

C o l u mn 1 i n e 2 8, c h a n 6 DeG rout to De G roof Signee and sealed this 6th day of March 1973. 1 1

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-1050H0-69) USCOMM-DC 60376-P69 U S. GOVERNMENT PRINTING OFFICE T 1969 O366334

Claims

1. A system for locking the blades of a blasting machine, said machine having axially spaced discs separated by spacers and defining a throwing wheel normally mounted on a rotatable shaft, said discs having substantially radial grooves receiving the edges of said blades, wherein the improvement comprises: locking means mounted on said spacers and engageable with said blades to prevent outward movement thereof, said spacers being provided with apertures disposed transversely with respect to an adjacent blade, and said locking means including a plug having a portion thereof transversing said aperture and slideably mounted with respect to said spacer, and having a head normally disposed on the opposite side of said spacer from said blade.

4. A throwing wheel for a blasting machine, said wheel having at least one disc disposed with a peripheral edge, said disc being secured to a hub member and provided with radial grooves, said wheel also having blades disposed with a portion of at least one edge thereof received in one of said grooves, said wheel also having locking means adapted to secure said blades against the action of centrifugal force, wherein the improvement comprises: portions on said blades extending radially beyond said peripheral edge of said disc, said blade portions having an offset engageable with said peripheral edge to limit inward movement of said blades.