GB2092045A - Brazing machine for sintered carbide tipped circular sawblades - Google Patents

Abstract

A brazing machine for sintered carbide tipped circular saw blades. In order that carbide tips can be positioned in the body B of the circular sawblade with repeatable accuracy and with high speed operation, the machine includes a carrier member for transferring carbide tips from a tip magazine 54 to a location in which they are to be brazed in position on a blade blank, an initial movement of the carrier bringing the carbide tip into position within a tooth space TS of the blade blank where brazing metal on the tip is heated and brought to a liquid state and a tip seating surface SS of the blade blank is brought into overlying abutment with the top surface of the tip, a final movement of the carrier member then displacing the carbide tip along the tip seating surface of the blade blank and into engagement with an abutment surface AB within the tooth space of the blank. <IMAGE>

Description

SPECIFICATION Brazing machine for sintered carbide tipped circular sawblades The invention relates to brazing machines for sintered carbide tipped circular sawblades and has for its object to provide an improvement therein.

Various machines already exist for brazing the sintered carbide teeth of carbide tipped circular sawblades in position. However, for a variety of reasons none of these existing machines are completely successful. In some cases the known machines are difficult to operate. In other cases the carbide tips cannot be positioned in the body of the circular sawblade with repeatable accuracy or with the speed of operation required for economic production. The invention has as its object to provide a brazing machine for sintered carbide tipped circular sawblades which will at least alleviate some of the drawbacks associated with previously known machines of this kind.

According to the invention there is provided a brazing machine for sintered carbide tipped circular sawblades, the machine including carrier means for transferring successive carbide tips from a tip magazine to a location in which they are to be brazed in position on a blade blank, mounting means for mounting the blade blank with its axis at right angles to the direction of movement of the carrier member and for indexing the blade blank between successive brazing operations to bring the next tooth space of the blank into a position for receiving the next carbide tip to be delivered, means for heating the carbide tip and a peripheral portion of the blank when said tip has been brought into the approximate position in which it is to be brazed in position, and means for controlling the movement of the carrier member and the mounting means for the blade blank whereby an intial movement of said carrier member brings the carbide tip into position within a tooth space of the blade blank, where brazing metal of the tip is heated and brought to a liquid state and a tip seating surface of the blade blank is brought into overlying abutment with the top surface of the tip, and whereby a final movement of said carrier member displaces the carbide tip along the tip seating surface of the blade blank and into engagement with an abutment surface within the tooth space of the blade blank. The machine may also include means for dispensing a dose of brazing compound onto a carbide tip being transferred on said means.The carrier member will preferably be in the nature of a slidable block element with means at a leading end for the reception of a carbide tip. The means at the leading end of the slidable block element for the reception of a carbide tip will preferably be constituted by a tip holder made of a ceramic material and provided with a slotted location for the tip, said slotted location pref erably having inclined side surfaces for guid ing a tip into position in the holder as it descends from the tip magazine and prefera bly having a tapering end portion for centralis ing the tip when said tip is urged rearwardly of the holder.A resilient finger may be ar ranged to ride lightly on the top surface of the tip holder as the latter is advanced so that this urges each tip rearwards into abutment with the tapering end portion of the slotted location as said tip is transferred to the location in which it is to be brazed in position on a blade blank. If the machine includes means for dispensing a dose of brazing compound onto a carbide tip being transferred on said carrier means, the slidable block element or guide bar slidably mounted for traverse movement therewith may be acted upon by resilient detent means, conveniently a spring loaded ball member capable of engaging a dimple or groove, so that a carbide tip can be brought to a halt for a brief period beneath the means for for dispensing the dose of brazing compound thereon.The mounting means for the blade blank may include a carriage arrangement slidably mounted along a guide track whereby an adjustment can be made to suit the diame ter ter of the circular sawblade blanks which are to be mounted thereon, said guide track pref erably being constituted by a pair of guide rods. An adjusting screw will preferably be provided for adjusting the carriage arrange ment ment along the guide track. A further adjust ing screw will preferably be provided whereby the inclination of the guide track can be adjusted to suit the geometry of the sawblades which are to be produced, that is to to say the rake angle at which the carbide tips are to be set in position in the blade blanks.A graduated scale may be provided to indicate the angular inclination of the guide track and the rake angle at which the carbide tips are to be set in position in the blade blanks. The mounting means for the blade blank will pref erably also include slipping clutch drive means so that when the brazing metal has been heated and brought to a liquid state the tip seating surface of the blade blank can be held in overlying abutment with the top sur face of the tip with a controlled pressure.

Such slipping clutch drive means may be driven by a rack and pinion arrangement, one of the rack element thereof being connected to a double acting pneumatic ram for traver sing the rack to and fro. In this case, the other end of the rack element may be con nected to a variable damper device for adjust ing the rate of traverse of the rack. The carrier member for transferring successive tips from the tip magazine to the location in which they are to be brazed in position will preferably be powered by a pneumatic ram, preferably a I double acting ram forming part of a pneuma tic control system including a pilot thruster valve associated with an adjustable damper device for adjusting the rate of response of said thruster valve opening and closing signals.

In order that the invention may be fully understod and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a side view of a brazing machine embodying the invention, Figure 1A is a scrap view, partly in section and drawn to a larger scale than Fig. 1, of a part of the machine shown in Fig. 1, Figures 2A and 2B form together a plan view of the machine, Figure 3 is a perspective view of a part of the machine, Figure 4 is a diagrammatic view showing a carbide tip being presented to a blade blank for brazing, Figures 5 to 7 are side, plan and end views of a carbide tip holder forming a part of the machine, and Figure 8 is a diagrammatic illustration of the pneumatic circuit of the machine, Referring now to the drawings, the brazing machine there illustrated is designed for brazing sintered carbide tips to circular sawblades.

The machine includes a base 10, a main support frame 12 carried by the base, mounting means generally indicated 14 for a blade blank which is to be provided with carbide tips, and mechanism generally indicated 16 for feeding the barbide tips in turn towards the blade blank concerned and for effecting the brazing operations.

The mounting means 14 comprise a carriage arrangement 18 slidably mounted on a guide track constituted by a pair of guide rods 20. A bracket 22, depending from the carriage arrangement 18, contains a nut (not shown) through which an adjustment screw 24 extends. The guide rods 20 extend outwards from and are rigidly connected to a support plate 26 which is pivotally connected to the support frame 12 about the axis of a shaft 27. The adjustment screw is rotatably mounted in the support plate 26 but is axially fixed with respect thereto.The ends of the guide rods remote from the support plate 26 are rigidly connected to an outer support plate 28 and that end of the adjustment screw extends rotatably through a depending part of the said outer support plate and is provided with a hand wheel 30 by means of which the carriage arrangement can be adjusted in position along the guide rods towards or away from the main support frame. The outer support plate 28 is in addition provided with a pair of side plates 92 between which a trunnion block 94 is pivotally mounted, said trunnion block providing a mounting and an axial location for an upper end of a further adjusting screw 96 the other end of which extends through a trunnion mounted nut 98 located in a bracket 100 projecting from the machine base. (The machine base is slotted to allow a lower end portion of the adjusting screw 96 to project into it as shown in Fig. 1).The upper end of the adjusting screw 96 is provided with a handwheel 102 and the arrangement is such that by turning said screw the inclination of the guide rods 20 can be adjusted.

Referring now in particular to Figs. 2A and 2B, the carriage arrangement is provided with means for mounting a circular sawblade blank and for indexing the blank between successive carbide tip brazing operations, said means including a rotatably mounted drive shaft 32, clamping means generally indicated 34 for securing a blade blank on said drive shaft, a slipping clutch unit generally indicated 36, and drive means generally indicated 38 for driving said drive shaft via said slipping clutch unit.

The clamping means for securing a blade blank of the drive shaft include a cone element 40 and a quick release nut element 42 both of which can be rmoved from a screwthreaded end portion 44 of the drive shaft when a completed sawblade is to be removed from the machine. Successive blade blanks can be mounted in position on the drive shaft, in abutment with a shoulder 46, ans centralised by the engagement of the cone element with the bore of the blank. In addition to the clamping means just referred to for securing a blade blank on the drive shaft, there are provided further blade clamping means in the form of an oppositely disposed pair of abutment member which are caused to act against the opposite side surfaces of the blade at locations adjacent the region in which a carbide tip is to be brazed in position.The abutment members include a linkage mounted abutment member 78 which is a fixed abutment in the sense that it is brought into position when a fresh blade blank has been mounted on the drive shaft and is not then relocated in an inoperative position until all the teeth of the blade blank have been provided with carbide cutting tips and the finished blade is to be removed from the drive shaft. A hand lever 80 is provided for operating the linkage by means of which the abutment member 78 is moved to and from its operative position. The other abutment member is an axially slidable rod 82 projecting from a carrier member 84. One side of said carrier member can be acted upon by the piston rod 86 of a pneumatic ram 88 to cause the blade clamping means to be applied. The other side of said carrier member is acted upon by a coil compression spring 90 which is arranged to retract the rod 82 when air under pressure has been exhausted from the pneumatic ram 88. The drive means 38 for driving the dria shaft via the slipping clutch unit includes a rack and pinion drive 48, the rack element of which is connected to one end to a double acting pneumatic ram 50 by means of which it can be traversed in opposite directions to rotate the drive shaft and at its other end to an adjustable damper device 52 by means of which the rate of travel of said rack element can be adjusted.

Referring now in particular to Figs. 1 and 1A, the machine is also provided with carrier means for transferring successive carbide tips from a tip magazine 54 to a location in which they are to be brazed in position on a blade blank, said carrier means including a slidable block element constituted by a tip holder bar 56 which is slidably mounted in the main support frame 12 and which can be advanced and retracted by means of a double acting pneumatic ram 58. A tip holder housing 60 is carried at one end of the tip holder bar, and a tip holder 62, made of a ceramic material, is carried by the housing 60.The tip holder, as best shown in Figs. 5 to 7, is provided with a slotted location 64 for a sintered carbide tip, the slotted location being provided with inclined side surfaces 66 for guiding a tip into position in the holder as it descends from the magazine 54, and being provided with a tapering end portion 68 by means of which a tip which has been intially located in position in the holder can be centraiised therein when urged rearwardly of the holder into abutment with said tapering end portion. A resilient finger 70, located adjacent the tip magazine, is arranged to ride lightly on the top surface of the tip holder housing and bar 56 as the latter is advanced and retracted.This urges each tip rearwards into abutment with the tapering end portion of the slotted location as said tip is transferred to the location in which it is to be brazed in position on a blade blank.

Between the tip magazine and the location in which the tips are brazed in position on a blade blank there are provided means for dispensing a dose of brazing compound (in the form of a paste) on a carbide tip being transferred on the tip holder, said means being constituted by a dispense unit 72 to which a pneumatic pressure can be applied to force a dose of the brazing compound from a nozzle 74. In operation of the machine, the tip holder is caused to pause in its forward travel from the tip magazine so that the dose of brazing compound can be applied to the top surface of the carbide tip concerned.So that the tip holder bar 56 can be caused to pause in exactly the correct position for the dose of brazing compound to be applied to the top surface of the carbide tip being transferred, a tip holder guide bar 104, which is slidably mounted in the main support frame for traverse movement with the tip holder bar, is provided with a dimple in which a spring ioaded ball member 106 (see Fig. 28) is engaged at a precise moment in its travel to act as a resilient detent. The guide bar 104 is also provided with a depending stop member 108 from which projects an adjustable screw 110 constituting an abutment member for contacting a traverse stop device, the latter being constituted by the piston rod 112 of a pneumatic ram 114.

Referring now in particular to Fig. 3, the machine is provided in the region of the location in which the carbide tips are to be brazed in position on a blade blank, with electrical heating means generally indicated 76, that is to say high frequency induction coils, for heating the carbide tip and a peripheral portion of the blade blank. As shown in Fig. 4, a blade blank indicated B is provided with tooth spaces TS and with respective tip seating surfaces SSterniinating in respective abutment surfaces AB.The arrangement is such that, in operation of the machine, a carbide tip is brought to the position indicated in chain-dotted lines in Fig. 4; the blade blank is turned so that the tip seating surface concerned is brought into overlying abutment with the top surface of the tip (or with the dose of brazing compound lying on said tip); the carbide tip and the adjacent area of the blade blank are heated by the heating means as the slipping clutch unit acts to apply a predetermined pressure to hold the seating surface of the blade blank against said tip; and finally, when the brazing compound has become melted, the carbide tip is moved by the tip holder through a further increment of movement along the tip seating surface of the blade blank and into engagement with the abutment surface AB, as shown in full lines, at which point the brazed joint is allowed to cool.When the brazed joint has been allowed to cool sufficiently for the carbide tip to be firmly attached to the blade blank, the tip holder bar 56 and with it the housing 60 and tip holder 62 are retracted to an intial starting position in readiness to receive a further carbide tip from the tip magazine and the blade blank is indexed around to bring the next tooth space into a position for receiving the advancing further carbide tip.

Referring now to Fig. 8, the pneumatic circuit of the machine is there illustrated in diagrammatic manner and includes a pilot thruster valve 116 associated with an adjustable damper device 118 for adjusting the rate of response of said thruster valve to opening and closing signals. (The thruster valve is a spring returned spool type valve and an opening signal is applied by air under pressure being ducted thereto through an air line 120.

A closing signal is applied by the exhaust of air from said air line 120). Air under pressure can be ducted through air lines 122 and 124, to and from the opposite ends of the pneumatic ram 58, to advance or retract the tip holder bar 56, according to the setting of the thruster valve, the rate of flow of air through the air lines being dependent on the setting of flow control valves 126 and 128.

In addition to the valves referred to above, the pneumatic circuit includes solenoid operated sequence valves 130, 132, 134, and 136, pilot valve 138 and regulator valves 140. The arrangement is such that in operation of the machine the tip holder 64 is beneath the tip magazine 54 and will have received a carbide tip at the beginning of a forward stroke of the pneumatic cylinder 58.

A signal is then given to extend the ram to bring the tip holder beneath the nozzle of the brazing compound dispense unit 72, the ram being temporarily locked in this position by the spring loaded ball element 106 engaging the dimple in the tip holder guide bar. A signal applied to the valve 116 will have closed off both of the air lines 122 and 124 during the brief pause of the tip holder beneath the nozzle of the dispense unit. A further signal applied to the valve 116 will open it relatively slowly against the pressure of the damper device 11 8 to that the slowly re-started forward movement of the tip holder will cause the brazing compound applied to the top surface of the carbide tip concerned to be broken away cleanly from the nozzle of the dispense unit.

The forward movement of the tip holder is arrested when the abutment member 110 contacts the piston rod 11 2 of the pneumatic ram 114. The carbide tip will now be in the position indicated in chain-dotted lines in Fig.

4, and at this point a supply of air under pressure delivered from the sequence valve 134 to the pneumatic ram 50 will cause the rack and pinion drive 48 to rotate the blade blank concerned via the slipping clutch unit so that a tip seating surface thereof is brought into overlying abutment with the top surface of the tip. Simultaneously, the high frequency induction coils will be activated for a predetermined period of time to heat the carbide tip and an adjacent area of the blade blank and to melt the brazing compound.

At this stage in the operation, the sequence valve 130 will operate to direct air under pressure to the pneumatic ram 88, so that the blade clamping means are applied, and to exhaust air under pressure from the pneumatic ram 114. Consequently, the piston rod 112 will be allowed to retract and the tip holder will be able to be advanced by the ram 58 through the further increment of movement required to bring the carbide tip concerned into engagement with the abutment surface AB of the blade blank. The carbide tip is held in this position for a pre-determined short period of time so that the brazed joint is allowed to cool.

The cycle of operation is completed by the reversal of the sequence valves 130, 132, 136 whereby the blade clamping is released and the piston rod 112 is once again extended; the pneumatic ram 58 is retracted to bring the tip holder into position beneath the tip magazine once again so that a further tip can be received in the holder under the force of gravity, and the pneumatic ram 50 is driven in the reverse direction so that the blade blank concerned is appropriately indexed to bring the next tooth space into line with the tip holder. After a few seconds delay, ensuring that a further tip will have been received in the holder, the machine will be ready for a further cycle of operations.

It has been found that the brazing machine described above has been able to operate with a very high standard of reliability and that the carbide tips can be brazed in position at a very high rate of production, very securely and with a high standard of accuracy. This high degree of security and accuracy is thought to result from the way in which a dose of brazing compound is melted before the tip is moved through a final increment of movement to bring it into engagement with an abutment surface of the blade blank and to the manner in which the carbide tips are located in the tip holder.

Various modifications may be made. For example, the mounting means for the blade blank need not necessarily include slipping clutch drive means. Such drive means could be replaced by a permanently stalled electric motor (but additional means would then of course be required for indexing the blade blank). In fact, each of the penumatic rams referred to could be replaced by electric motor drive means suitably programmed for bringing about the timed sequence of movements referred to above. If pre-coated carbide tips are used, that is to say tips provided with a previously applied coating of brazing metal and flux, the dispense unit 72 for brazing compound will not be required.

The machine could be provided with a graduated scale to indicate the angular inclination of the guide track (but it will be understood that if this is to indicate also the rake angle at which the carbide tips are to be set in position in the blade blanks it will be necessary to re-position the axis about which the guide track is adjustable; the axis will need to be moved from the position shown in Fig. 1 so that it passes through the location in which the carbide tips are brazed in position on a blade blank).

The clamping means 34 for securing a blade blank of the drive shaft 32 could be designed so that when the damping means have been released the threaded end portion of the drive shaft extends no further outwards, or virtually no further outwards, than the shoulder 46. In this way the blade blank is enabled to be removed from the machine arlo another one mounted in position by a sliding movement in the piane of tho shoulder. Con sequently, in this case the abutment member can be permanently fixed in position and the hand lever 80 will no longer be required.

The pneumatic circuit of the machine could be arranged somewhat differently than as described with reference to Fig. 8; in paricular it may be re-designed in a manner making the provision of the spring loaded ball element 106 engaging the dimple in the tip holder guide bar unnecessary.

Claims (18)

1. A brazing machine for sintered carbide tipped circular sawblades, the machine including carrier means for transferring successive carbide tips from a tip magazine to a location in which they are to brazed in position on a blade blank, mounting means for mounting the blade blank with its axis at right angles to the direction of movement of the carrier member and for indexing the blade blank between successive brazing operations to bring the next tooth space of the blank into a position for receiving the next carbide tip to be delivered, means for heating the carbide tip and a peripheral portion of the blade blank when said tip has been brought into the approximate position in which it is to be brazed in position, and means for controlling the movement of the carrier member and the mounting means for the blade blank whereby an intial movement of said carrier member brings the carbide tip into position within a tooth space of the blade blank, where brazing metal on the tip is heated and brought to a liquid state and a tip seating surface of the blade blank if brought into overlying abutment with the top surface of the tip, and whereby a final movement of said carrier member displaces the carbide tip along the tip seating surface of the blade blank and into engagement with an abutment surface within the tooth space of the blade blank.

2. A brazing machine according to claim 1, in which the machine also includes means for dispensing a dose of brazing compound onto a carbide tip being transferred on said carrier means.

3. A brazing machine according to either one of the preceding claims, in which the carrier member is in the nature of a slidable block element with means at a leading end for the reception of a carbide tip.

4. A brazing machine according to claim 3, in which the means at the leading end of the slidable block element for the reception of a carbide tip are constituted by a tip holder made of a ceramic material and provided with a slotted location for the tip.

5. A brazing machine according to claim 4, in which the slotted location for the carbide tip in the tip holder has inclined side surfaces for guiding a tip into position in the holder as it descends from the tip magazine and has a tapering end portion for centralising the tip when said tip is urged rearwardly of the holder.

6. A brazing machine according to claim 5, in which a resilient finger is arranged to ride lightly on the top surface of the tip holder as the latter is advanced so that this urges each tip rearwards into abutment with the tapering end portion of the slotted location as said tip is transferred to the location in which it is to be brazed in position on a blade blank.

7. A brazing machine according to any one of claims 3 to 6, in which the machine includes means for dispensing a dose of brazing compound onto a carbide tip being transferred on said carrier means, and the slidable block element or a guide bar slightly mounted for traverse movement therewith is acted upon by resilient detent means, conveniently a spring loaded ball member capable of engaging a dimple or groove, so that a carbide tip can be brought to a halt for a brief period beneath the means for dispensing the dose of brazing compound thereon.

8. A brazing machine according to any one of the preceding claims, in which the mounting means for the blade blank include a carriage arrangement slidably mounted along a guide track whereby an adjustment can be made to suit the diameter of the circular sawblade blanks which are to be mounted thereon.

9. A brazing machine according to claim 8, in which the guide track is constituted by a pair of guide rods.

10. A brazing machine according to either one of claims 8 and 9, in which an adjusting screw is provided for adjusting the carriage arrangement along the guide track.

11. A brazing machine according to claim 10, in which a further adjusting screw is provided whereby the inclination of the guide track can be adjusted to suit the geometry of the sawblades which are to be produced, that is to say the rake angle at which the carbide tips are to be set in position in the blade blanks.

12. A blazing machine according to claim 11, in which a graduated scale is provided to indicate the angular inclination of the guide track and the rake angle at which the carbide tips are to be set in position in the blade blanks.

13. A brazing machine according to any one of claims 8 to 12, in which the mounting means for the blade blank also include slipping clutch drive means so that when the brazing metal has been heated and brought to a liquid state the tip seating surface of the blade blank can be held in overlying abutment with the top surface of the tip with a controlled pressure.

14. A brazing machine according to claim 13, in which the slipping clutch drive means are driven by a rack and pinion arrangement, one end of the rack element thereof being connected to a double acting pneumatic ram for traversing the rack to and fro.

15. A brazing machine according to claim 14, in which the other end of the rack element is connected to a variable damper device for adjusting the rate of traverse of the rack.

16. A brazing machine according to any one of the preceding claims, in which the carrier member for transferring successive carbide tips from the tip magazine to the location in which they are to be brazed in position is powered by a pneumatic ram.

17. A brazing machine according to claim 16, in which the pneumatic ram for powering the carrier member is a double acting ram forming part of a pneumatic control system including a pilot thruster valve associated with an adjustable damper device for adjusting the rate of response of said thruster valve to opening and closing signals.

18. A brazing machine constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.