EP0084430B1

EP0084430B1 - Improvements in or relating to shot blast machinery

Info

Publication number: EP0084430B1
Application number: EP83300143A
Authority: EP
Inventors: William Robertson Macmillan
Original assignee: Tilghman Wheelabrator Ltd
Current assignee: Tilghman Wheelabrator Ltd
Priority date: 1982-01-16
Filing date: 1983-01-12
Publication date: 1986-07-23
Also published as: ATE20845T1; DE3364555D1; GB2113127B; EP0084430A1; GB8300758D0; GB2113127A

Abstract

A lining assembly for a hood for housing an abrasive throwing wheel cornprises two end wearplates, two side wearplates of unitary or split construction, and an upper wearplate with integral sides, all butted together to provide locating and labyrinthal joints and with each end wearplate being formed with at least one inwardly-directed wear projection or dam adapted to intervene in the flow path of abrasive accelerating around the hood thereby substantially to reduce the rate of wear on the wearplates by the abrasive.

Description

This invention relates to shot blast machinery and is particularly concerned with a lining assembly for the wheel hood of such machinery.
A wheel hood lining assembly, as is well known to those skilled in the art, consists of a multiplicity of wearplates which are assembled together inside a wheel hood to surround a rotatable abrasive throwing wheel housed in the hood and which serve to protect the wheel hood from attack by the abrasive accelerated around the hood by the throwing wheel prior to being impelled out through an open side of the hood.
These wearplates are formed of hard metal to give them a reasonably long working life but eventually they become worn and require replacement. An example of hard metal, which is a term well known to those familiar with the shot blast machinery industry, is that sold by the Applicants under the Trade Mark "BLASTLYFE" which is a high chrome alloy. They constitute a signficant part of the "spares" business in shot blast machinery.
Lining assemblies comprising various numbers of wearplates are well known to those skilled in the art.
Such assemblies of wearplates provide many joints through which abrasive may leak to cause wear in the wheel hood thus necessitating maintenance and eventual replacement with consequent cost to the user.
In an effort to overcome this drawback proposals have been made to reduce the number of wearplates in a lining assembly and consequently the number of joints. Also, such joints are often made labyrinthal to impede leakage of abrasive therethrough.
Examples of such lining assemblies are known from DE-AI-2437493 which discloses a lining assembly consisting of two end wearplates, two side wearplates and an upper wearplate, and from US-A-3800474 which discloses two end wearplates, two multi-part side wearplates and an upper wearplate with the joints between the wearplates being of labyrinthal configuration.
The present investigation is concerned with such a lining assembly comprising a reduced number of wearplates with labyrinthal joints between the wearplates but with the added advantages of reducing the rate of wear on each end wearplate in particular and providing end wearplates which increases the blasting efficiency of a rotating abrasive throwing wheel housed in a hood fitted with a lining assembly according to this invention.
According to a first aspect of the present invention, therefore, there is provided a lining assembly for a hood for use in shot blast machinery and adapted to house a rotatable throwing wheel for centrifugally impelling abrasive out through an open side of the hood in the direction of a workpiece to be cleaned, the lining assembly consisting of two side wearplates, two end wearplates, and an upper wearplate adapted to be arranged within the hood with their adjacent edges in butted relationship to cover and thereby protect the inner wall surfaces of the hood without impeding the open side of the hood and with their butting edges configured to define locating the labyrinthal joints, and being characterised in that each end wearplate is formed with at least one inwardly-directed projection or dam which, when the end wearplates are fitted inside the hood with the rotatable throwing wheel housed therein, extends into the flow path of abrasive accelerated around the hood by the throwing wheel prior to being impelled out through the open side thereof by the latter thereby substantially to reduce the rate of wear on the end wearplate, and which is directed towards the open side of the hood so as to direct abrasive striking same to be returned into the normal abrasive pattern created by the rotating throwing wheel thereby to substantially reduce abrasive rebound within the hood and consequently to increased blasting efficiency.
It will be manifest that, with both end wearplates provided with such wear projections or dams, the wear dams of the leading end wearplate in terms of direction of wheel rotation (i.e. the lefthand end wearplate for a clockwise rotating throwing wheel) will serve to impede at least some of the abrasive which is normally carried round by the high speed rotating wheel (several thousand r.p.m.).
It is this abrasive which accelerates round the hod which does the wear damage. The abrasive includes particles of different sizes and the finer particles are those which do most damage by scouring away the wearplates. Some of the coarser and thereby heavier abrasive particles fall back into the throwing wheel as they pass through the hood.
The upper wearplate may be formed with at least one inwardly-directed wear dam which extends into the flow path of the accelerating abrasive to decelerate same and/or cause at least some to be directed away from the wearplate and back towards the throwing wheel. Such wear dam(s) on the upper wearplate are more likely to be omitted than provided.
Preferably the upper wearplate at each end has an inwardly-directed formation which cooperates with a complementary inwardly-directed formation at the top of each end wearplate to constitute another wear dam.
The number and configuration of the wear dams can be varied provided they function to resist the wear effect of abrasive accelerating around the hood, and provided they return such abrasive into the abrasive pattern of the throwing wheel to reduce reboound and to increase blasting efficiency.
The side wearplates, whether unitary or in two halves, are preferably of trapezium configuration with the usual hole for either the central infeed of abrasive to the throwing wheel or connection of the driving motor to the wheel directly or through the intermediary of a bearing housing.
Another aspect of the invention is an end wearplate as claimed in claim 13.
An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a side sectional view of a hood, hood lining and abrasive throwing wheel, the hood lining being in accordance with the present invention;
Fig. 2 is a transverse sectional view on the line II-II of Fig. 1;
Figs, 3, 4 and 5 are respectively a front elevation, a longitudinal sectional view and a transverse sectional view to an enlarged scale of an end wearplate, Fig. 5 also showing a modification;
Figs. 6, 7, 8 and 9 are respectively a front view, a bottom view, a sectional view on the line VIII-VIII of Fig. 6 and a sectinal view on the line IX-IX of Fig. 6 of a side wearplate;
Figs. 10 and 11 are respectively a longitudinal sectional view and a half-sectional view of an upper wearplate;
Fig. 12 is a sectional view to an enlarged scale on the line XII-XII of Fig. 1, illustrating a labyrinth joint between adjacent wearplates;
Figs. 13 and 14 are sectional detail views of alternative mating configurations of an end wearplate and upper wearplate; and
Fig. 15 is a half-sectional view of a hood and a hood lining according to the invention.

Referring firstly to Figs. 1 to 12, the hood is generally indicated by the reference 20 and the abrasive throwing wheel by the reference 21. Both of these are of well-known construction to those skilled in the art and will not be described further.
The lining for the hood, in this instance, consists of two side wearplates 22, two end wearplates 23 and an upper wearplate 24.
The side wearplates 22 are of trapezium configuration and have a substantially centrally disposed circular hole 25, one for abrasive entry as indicated at 25A in Fig. 2 and the other for motor or bearing house connection as indicated at 25B in Fig. 2. As aforesaid, each side wearplate 22 may consist of two halves, the split line being indicated at 26 in Fig. 6. The two halves form a butt connection along this line 26.
The side wearplates 22 have recessed areas 27 for weight reduction and four screw-threaded studs 28 for use in securing them to the side walls of the hood 20.
As can be seen the edges of the side wearplates 22 are configured to cooperate with the edges of the end wearplates 23 and the upper wearplate 24 to make labyrinth joints as exemplified at 29 in Fig. 12. These joints resist abrasive leakage in addition to relatively locating the wearplates making up a hood lining and are well known to those skilled in the art.
Each end wearplate 23 which is channel shaped is formed with two wear dams 30 on its internal face and a pair of locating lugs 23L on its external face. The wear dams 30 are, in this embodiment, a pair of spaced inwardly and downwardly directed flanges, that nearer the bottom being smaller than the other. At its top end, each end wearplate 23 has an inwardly-directed projection 31 which cooperates with a complementary formation 32 on the end of the upper wearplate 24 to provide a wear dam (see Fig. 1).
The upper wearplate 24 has integral sides 33 so that it is channel shaped (see Fig. 2) and in addition to end formations 32 has a centrally disposed cross flange 34 connecting its sides and forming a wear dam. The upper wearplate 24 has on its external face two tapped bosses 35 for locating purposes.
The wearplates are assembled together to form a lining for the hood 20 as shown and screws or bolts 36 and 37 passing through the hood 20 engage between lugs 31 and in the bosses 35 to locate end wearplates 23 and the upper wearplate 24 of the assembly. The screw-threaded studs 28 are employed to secure the side wearplates in position.
The wearplates are, of course, dimensioned to fit into different-sized and different constructions of wheel hoods. For example wheel hoods for accommodating different diameter throwing wheels.
Such hoods, see 20 in Fig. 1, have removable lids for removal and insertion of worn and fresh wearplates and, of course, the throwing wheel, see 21 in Fig. 1. A seal strip 38 is clamped between hood 20 and lid 37.
The wearplates must therefore be dimensioned and configured to permit such removal and insertion.
With the throwing wheel 11 in clockwise operation, accelerating abrasive carried round by the wheel firstly encounters the wear dams 30 of the lefthand end wear^plate 23 which causes some of the abrasive to fall back into the abrasive pattern of the wheel and decelerates some more of the abrasive. A similar action is effected by wear dams 34 and 31, 32. The remaining accelerating abrasive impinges on the wear dams 30 of the righthand end wearplate 23 and is largely diverted thereby into the wheel abrasive pattern.
It is to be noted that, in general, the wear dams will become worn before the main body of the wearplates.
In Fig. 13 like parts as illustrated in Figs. 1 to 12 are referenced with the same numerals with the suffix "A", and in Fig. 14 with the suffix "B".
In these two instances, it can be seen that the formations 31A, 32A and 31B, 32B differ from formations 31, 32 but still provide the labyrinth and locating joint and the wear dam.
The wearplates of Fig. 13 are configured for a different hood to that used with the wearplates of Fig. 4 but, in each case, the configurations allow removal and insertion through the open top of the hood.
Referring now to Fig. 15, like parts to Figs. 1 to 12 are referenced with the numerals with the suffix "C". Here, we will describe only the differences between the two embodiments.
It will be noted that the locating lugs 31 are omitted from the end wearplate 23C, the locating bolt 36C still however engaging the wall of the end wearplate 23C.
The end wearplate 23C is, in this instance, formed with a shielding flange 39 (see also Fig. 5) which serves to impede abrasive tending to bounce up the back of the end wearplate 23C. Such shielding flange may be provided on any of the end wearplates hereinbefore referred to.
The shielding flange 39 may be nearer the bottom of the end wearplate, in which case, it is smaller, or it may be at the bottom edge of the end wearplate.
The upper wearplate 24C may be clamped to the end wearplates 23C via bosses 40 and spring or other clips (not shown) instead of being located by bolts or screws 37.
In this instance, it can be seen that the hood 20C has straight sides, the lid 36C being dish-shaped and retained in position by bolts 41 and wing nuts 42.

Claims

1. A lining assembly for a hood (20) for use in shot blast machinery and adapted to house a rotatable throwing wheel (21) for cetrifugally impelling abrasive out through an open side of the hood (20) in the direction of a workpiece to be cleaned, the lining assembly consisting of two side wearplates (22), two end wearplates (23), and an upper wearplate (24) adapted to be arranged within the hood (2) with their adjacent edges in butted relationship to cover and thereby protect the inner wall surfaces of the hood without impeding the open side of the hood (20) and with their butting edges configured to define locating and labyrinthal joints (29), and being characterised in that each end wearplate (23) is formed with at least one inwardly-directed projection or dam (30) which, when the end wearplates (22) are fitted inside the hood (20) with the rotatable throwing wheel (21) housed therein, extends into the flow path of abrasive accelerated around the hood (20) by the throwing wheel (21) prior to being impelled out through the open side thereof by the latter thereby substantially to reduce the rate of wear on the end wearplate (22), and which is directed towards the open side of the hood (20) so as to direct abrasive striking same to be returned into the normal abrasive pattern created by the rotating throwing wheel (21) thereby to substantially reduce abrasive rebound within the -hood (20) and consequently to increased blasting efficiency.

2. A lining assembly as claimed in claim 1, comprising two or more such inwardly-directed formations or dams (30) spaced along the length of the end wearplate (23).

3. A lining assembly as claimed in claim 2, in which the projections or dams (30) decrease in length the nearer they are to the hood opening when the end wearplate (23) is fitted in the hood (20).

4. A lining assembly as claimed in any one of claims 1 to 3 in which each end wearplate (22) has at its hood opening remote end an inwardly-directed formation (31) adapted to cooperate with a complementary inwardly-directed formation (32) at the abutting end of the upper wearplate (24) to define an inwrdly and downwardly wear projection or dam (31, 32).

5. A lining assembly as claimed in any one of claims 1 to 4 in which each end wearplate (23) is of channel section.

6. A lining assembly as claimed in any one of claims 1 to 5 comprising a pair of spaced locating lugs (23L) on the face of each end wearplate (23) remote from the wear formation(s) or dam(s), which lugs are adapted to receive a locating and securing bolt or screw (36) carried by the hood (20).

7. A lining assembly as claimed in any one of claims 1 to 6 in which each end wearplate 23 has on its face adjacent the hood when the end wearplate is fitted therein, a shielding flange (39) adapted to impede the passage of abrasive between said face and the hood (20).

8. A lining assembly as claimed in any one of claims 1 to 7, in which the upper wearplate (24) has at least one wear projection or dam (34) inwardly directed to extend into the flow path of the accelerating abrasive to decelerate same and/ or cause at least some to be directed back towards the rotating throwing wheel.

9. A lining assembly as claimed in any one of claims 1 to 8, in which the upper wearplate (24) is of channel configuration with integral sides (33).

10. A lining assembly as claimed in any one of claims 1 to 9, in which the upper wearplate (24) has on its external, i.e. hood-adjacent, face two tapped bosses (35) for receiving locating and securing bolts or screws (37) carried by the hood (20).

11. A lining assembly as claimed in any one of claims 1 to 10 in which each side wearplate (22) consists of two half wearplates butted together along a line normal to the top and bottom of the hood (20) when the side wearplate (22) is fitted therein.

12. A lining assembly as claimed in any one of claims 1 to 11 in which each side wearplate (22) has a central hole (25) and also has screw-threaded studs (28) for securing same to the side wall of the hood (20).

13. An end wearplate of a lining assembly for a hood (20) for use in shot blasting machinery and adapted to house a rotatable throwing wheel (21) for centrifugally impelling abrasive out through an open side of the hood (20) in the direction of a workpiece to be cleaned, the end wearplate (23) being characterised in that it is formed with at least one projection (30) on its face adjacent the throwing wheel (21) when it is fitted inside the hood (20), which projection (30) extends into the flow path of abrasive accelerated by the throwing wheel (21) and is directed towards the open side of the hood whereby the rate of wear on the end wearplate (23) is reduced and abrasive is redirected by the projection or dam (30) into the abrasive pattern so as to eliminate abrasive rebound and so increase blasting efficiency.

14. The combination of a hood (20) for use in shot blasting machinery and adapted to house a rotatable throwing wheel (21) for centrifugally impelling abrasive out through an open side of the hood (20) in the direction of a workpiece to be cleaned, and a lining assembly of wearplates (22, 23 and 24) as claimed in any one of claims 1 to 12 fitted within the hood (20).