GB2144062A - Workpiece mounting arrangement - Google Patents

Abstract

A workpiece mounting arrangement comprises a vice with associated elements (7a, 7b), known as "parallels", for locating a workpiece at a required height above the vice table (3). To avoid the need to make the parallels (7a, 7b) thick enough to be free-standing, magnets (12) or other force-applying means are provided to hold the parallels (7a, 7b) against the vice jaws (2b, 5b). This arrangement enables narrow parallels (7a) to be used so that the danger of the parallels being damaged during the drilling of holes through the workpiece is minimal. The force-applying means (12) is so arranged that, for the or each movable jaw (5b, 5), the associated parallel (7a) can move over the jaw face; this permits the workpiece and parallel to be properly seated on the vice table (3). A vice having magnetically held jaw faces is also disclosed. <IMAGE>

Description

SPECIFICATION Workpiece mounting arrangement The present invention relates to a workpiece mounting arrangement of the type comprising a vice with associated elements, known as "parallels", for locating a workpiece at a required height in the vice. Mounting arrangements of this type are often used with machine tools to set up for machining a succession of identical workpieces.

A prior art workpiece mounting arrangement of the aforesaid type is illustrated in Figures 1 to 3 of the accompanying drawings, Figure 1 being a side elevation of the mounting arrangement Figure 2 a section taken on line II of Figure 1, and Figure 3 a side elevation similar to Figure 1 but showing a workpiece being clamped in position. As can be seen from Figures 1 and 2, the vice of the mounting arrangement comprises a vice body 1 defining a vice table 3, a fixed jaw 2, a movable jaw 5 sliding in a guideway 10, and suitable means, such as a screw mechanism 11, for advancing and withdrawing the movable jaw 5 relative to the fixed jaw 2. In order to locate a workpiece in the vice at a desired machining height, two seating blocks 7, known as parallels 7, are provided which serve to support the workpiece W at a known height above a datum constituted by the surface of the vice table 3.The parallels 7 have parallel top and bottom surfaces and are of equal heights. The thickness of the parallels 7 is such that they are free standing on the table 3 while their length is generally greater than the width of the table 3.

In use of the mounting arrangement parallels 7 of the desired height are first selected and placed on the vice table 3; thereafter the workpiece W is seated on the parallels 7 and the jaw 5 is closed up in the direction of arrow A in Figure 3 to clamp the workpiece W in position for machining. Generally, due to the slight vertical play present in the coupling between the jaw 3 and guideway 10, during the closing movement the clamping reaction force exerted on the jaws 3 will cause the latter to lift up slightly (see arrow B). As a result, it is necessary to tap the workpiece W down onto the parnllels 7 as is indicated by arrow C in Figure 3.

This known mounting arrangement suffers from a number of disadvantages: before each workpiece is loaded, it is necessary to remove the parallels 7 from the vice and both the parallels and the vice must be cleaned to ensure that no swarf or dirt is interposed between the vice table 3 and the parallels 7, or between the parallels 7 and the workpiece W; -if any holes are to be machined completely through the workpiece W, then either the parallels 7 must be carefully positioned to ensure that the cutting tool does not touch them (this can be difficult or even impossible), or they must be removed before the throughhole is machined;; it is easy, when tapping the workpiece W down to ensure proper contact with the parallels 7, to strike the workpiece outside the bounds of the vice table 3 thus tilting the parallels 7 in the vice.

In order to overcome the above disadvantages associated with parallels, it is known to machine each vice jaw to provide a step, the jaws then serving both to grip the workpiece and support it at the correct level. However, this arrangement suffers from the disadvantage. that it does not enable proper compensation to be made for the lifting of the movable jaw that occurs upon closure of the vice, the amount of this lifting being variable and dependent upon the closing force applied. As a result, the bottom face of the workpiece will be out of parallel with the vice table. Furthermore, since in general it will be desired to set different workpieces at different heights relative to the vice table, this mounting arrangement requires a different set of machined jaws for each design of workpiece which is both time-consuming and expensive.

It is an object of the present invention to overcome at least some of the above-mentioned disadvantages of the prior art mounting arrangements.

According to one aspect of the present invention, there is provided a workpiece mounting arrangement comprising a vice-including a body, defining a vice table, and a pair of cooperating jaws at least one of which is displaceable towards the other jaw to enable a workpiece to be gripped therebetween; a pair of parallels for locating the workpiece at a desired height above the vice table; and forceapplying means for releasably holding the parallels against respective ones of the vice jaws, the force-applying means operating in a manner, in respect of the or each displaceable jaw, enabling the associated parallel to be moved over the face of the jaw.

Due to this arrangement, the parallels no longer need to be wide enough to be free standing since they are maintained upright by virtue of being held against the jaws. As a result, the parallels can be made from very narrow stock (as little as 0.4 mm) which, together with the fact that the parallels lie beneath the very edge of a workpiece, means that through holes can be machined virtually anywhere on the workpiece without the risk of meeting a parallel.

The facility for relative movement between the or each displaceable jaw and its associated parallel permits the parallel to be tapped down onto the vice table to overcome the lifting problem, described above,which occurs when the jaws are closed up on a workpiece.

Due to the retention of the parallels against the jaws, and due to the fact that upon opening of the vice the lifting effect is reversed so that the parallel associated with the or each displaceable jaw will be kept in contact with the vice table, the possibility of swarf entering between the parallels and the jaws and between the parallels and the vice table is virtually eliminated. As a result, after the machining of each workpiece in a machining run, it is only necessary to clear swarf from the top of the parallels, the working faces of the jaws and the operative area of the vice table (the parallels being left in position on the jaws).In fact, cleaning of the vice table can be dispensed with if the parallel associated with the or each displaceable jaw is kept in contact with the vice table on closure of the vice; this can be achieved either by arranging that the displaceable jaw does not "drop" when the vice is opened (so that on reclosure, no further lifting occurs), or by applying a downward bias force at least to the parallel associated with the or each displaceable jaw (whereby to hold the parallel down against any lifting effect experienced by the jaws upon closing).The former method of maintaining contact between parallel and vice table can be implemented by arranging for the force-applying means to hold the parallel against the vice face with sufficient force that the friction therebetween is sufficient to support the jaw in a lifted state; the latter method of maintaining parallel/vice table contact can be implemented with downward-bias means in the form of springs. By either of these methods the parallel associated with the or each displaceable jaw is kept in contact with the vice table and effects a sweeping action as the vice jaws close thereby ensuring that no swarf is present beneath the parallel. Of course, in practice, occasional cleaning of the vice table is necessary to avoid an excessive build up of swarf.

In a preferred embodiment of the invention, the force-applying means are constituted by magnets embedded in the face of the vice jaw, the parallels being made of a ferrous metal. The strength of the magnets is preferably selected to ensure that the parallel of the or each displaceable jaw will be kept in contact with the work table in the manner explained above. Alternatively, downward-bias means can be provided, for example, for the or each jaw provided with such means, by a spring-biased lever pivoted on the jaw and arranged to engage and apply a downwards force to the associated parallel.

In an alternative embodiment of the invention, the force-applying means and the downward-bias means are jointly constituted, for each parallel, by one or more tension springs attached at one end to the corresponding jaw and inclined upwardly for attachment at their opposite ends to the parallel whereby to draw the latter both against the jaw and downwardly.

Although in the embodiments described above, the force-applying means are primarily mounted on the vice jaws, it would of course be possible to mount the force-applying means primarily on the parallels though such an arrangement is not preferred since this would generally increase the cost of changing the parallels when machining requirements so dictate.

Where the parallels are-very narrow, it is desirable to form each parallel as a composite comprising a narrow primary parallel in contact with the workpiece and a wider, tableprotecting, secondary parallel interposed between the bottoms of the narrow parallels and the vice table. A composite parallel of this form ensures that when a workpiece is tapped down to properly seat it on the parallels, the narrow parallels do not form indentations in the vice table. The primary and secondary parallels of each composite parallel are preferably separately held against the corresponding jaw by the force applying means. Where downward-bias means are provided, these can be arranged to act solely on the narrow primary parallels, the downward bias force being, of course, transmitted to the table-protecting secondary parallels.

Generally, the parallels will project laterally of the vice jaws. To ensure that excessive build up of swarf behind the lateral portions of the parallels does not force the parallels away from the jaws as the latter are opened, it is preferable to provide the moving jaw or jaws of the vice with lateral wipers which serve to wipe away swarf from the regions behind the lateral portions of the parallel.

In order to avoid the risk of the parallels becoming tilted when a workpiece is tapped to ensure its proper seating, the vice body is preferably such that it provides two lateral wings extending on respective sides of the vice table and upon which the ends of the parallels are arranged to seat. Alternatively, the vice table itself may extend to the ends of the parallels, but this will only be possible with a split table in which the guideway for the movable vice jaw extends centrally through the table.

Various other novel aspects and features of the invention will become apparent from the following description, given by way of example only, of three workpiece mounting arrangements each embodying the invention and each comprising a vice and cooperating parallels, reference being made to the accompanying diagrammatic drawings, in which:: Figure 1 is, as previously described, a side elevation of a prior-art mounting arrangement; Figure 2 is, as previously described, a section taken on line ll-ll of Figure 1; Figure 3 is, as previously described, a side elevation similar to Figure 1 but showing a workpiece being clamped in position; Figure 4 is a side elevation of a first workpiece mounting arrangement embodying the invention; Figure 5 is a plan view of the Figure 4 arrangement; Figure 6 is a section on line VI-VI of Figure 4; Figure 7 is a section similar to Figure 6 but showing a different form of vice used in the mounting arrangement; Figures 8 and 9 are respectively a side elevation and a plan view of part of a second workpiece mounting arrangement embodying the invention; and Figures 10 and 11 are respectively a side elevation and a plan view of part of a third workpiece mounting arrangement embodying the invention.

Figures 1, 2, 3 relate to a prior art workpiece mounting arrangement which has already been described and will not be considered further hereinafter.

The first mounting arrangement embodying the invention is illustrated in Figures 4 to 6 and is constituted by a vice and a cooperating set of composite parallels.

The vice of the arrangement of Figures 4 to 6 comprises a vice body 1 defining a vice table 3, a fixed jaw 2 made up of a jaw block 2a and a replaceable hardened jaw element 2b, a movable jaw made up of a movable jaw block 5a and a replaceable hardened jaw element 5b, and means 11 for displacing the movable jaw 5 along a guideway 10 formed in the vice body 1. The means 11 for displacing the jaw 5 may be constituted by a screw mechanism (as illustrated) or any other suitable means such as an hydraulic or pneumatic actuator.

Associated with each jaw element 2b, 5b is a composite parallel made up of a narrow primary parallel 7a and a wider, table-protecting, secondary parallel 7b, the secondaryparallel 7b being interposed between the bottom of the primary parallel 7a and the vice table 3. The parallels7a, 7b are made of a ferrous material.

Four pot magnets 1 2 are embedded in the front face of each jaw element 2b, Sb, two of these magnets being disposed at the height of the primary parallel 7a and two at the height of the secondary parallel 7b. These magnets 12 serve to hold the parallels 7a, 7b against the jaw elements 2b, 5b. Since the parallels 7a no longer have to be self supporting, they can be made very narrow which substantially eliminates the risk of the parallels being struck by a cutting tool during the course of the machining of a through-hole in a workpiece seated on the parallel.

Since the parallels 7a, 7b are held firmly in contact with the jaw elements 2b and 5b, it is impossible for swarf and dirt to enter therebetween. Furthermore, since during machining and upon release of a workpiece from the vice, the parallels 7a will be firmly seated on the parallels 7b and the latter will be firmly seated on the table 3, then provided the operative area of the table 3 is cleared of swarf before the vice is closed up on a new workpiece, there exists no possibility for swarf or dirt to get underneath a parallel. As a result, it is unnecessary to remove the parallels 7a and 7b between machine operation.In fact, as already explained in principle, provided the strength of the magnets 1 2 is sufficient to ensure that the friction between the parallels 7a, 7b and the jaw element 5b is adequate to prevent the jaw 5 dropping upon opening of the vice, then the requirement to clean the vice table 3 between workpieces can be dispensed with.

The purpose of the table-protecting parallels 7b is to prevent damage to the table 3 which might otherwise occur upon tap down of a newly inserted workpiece as a result of the narrowness of the parallels 7a.

With a view to avoiding the possibility of tilting the parallels 7a, 7b as a workpiece is tapped down, the vice shown in Figures 4 to 6 is provided with lateral wings 1 3 the top surfaces of which lie in the same plane as the top of the table 3. These wings 1 3 serve to support the lateral extremities of the parallels 7a,7b and thereby prevent tilting of the latter.

The same effect can be achieved by using a split vice table (see Figure 7), this table being formed in two parts 3a, 3b which extend laterally as far as the parallels 7a, 7b: in this case, the guideway 10 for the movable jaw 5 lies between the two parts 3a, 3b, of the table. Since in the mounting arrangement shown in Figures 4 to 6 the parallels 7a, 7b project beyond the movable jaw 5, an excessive build-up of swarf behind the parallels 7a and 7b could result in these parallels being pushed out of contact with the jaw element 5b as the jaw 5 is moved backwards to release a machined workpiece. To prevent this happening, wiper blades 14 can be fixed to the movable jaw 5 to sweep away excessive swarf out of the path of the lateral extremities of the parallels 7a, 7b.

Use of the workpiece mounting arrangement of Figures 4 to 6 will now be briefly described starting from the condition in which the vice and parallels are clean. First of all, the parallels 7a and, if required, the parallels 7b are placed in their correct positions on the vice table 3 in contact with the jaw elements 2b and 5b. A workpiece (not shown in Figures 4 to 6) is then located in position resting on the parallels 7a and the movable jaw 5 is closed to grip the workpiece. Next, the workpiece is tapped down to ensure that all the faces between the workpiece and the table 3 are in contact, even though the movable jaw 5 may have lifted.

After the workpiece has been machined, the vice is opened to release the workpiece. As suming that the magnets 1 2 are of sufficient strength, the movable jaw 5 will not fall as it is moved back and the parallel or parallels will remain in contact with the jaw element 5b and the vice table. Thus, when the movable jaw 5 is moved back, swarf deposited during the machining operation cannot enter between the parallel (s) and the jaw or beneath the parallel (s).

After the machined workpiece is removed, the tops of the parallels and the gripping faces of the jaws are cleaned. Excess swarf elsewhere on the vice need only be removed to prevent clogging of the vice itself. Thereafter a new workpiece is introduced and the vice jaws closed again.

Instead of relying on the friction between the parallels and jaw 5 to keep the latter lifted and thereby prevent a gap opening up between the parallels and vice table 3, means can be provided to exert a downward bias force on the parallel or parallels associated with the movable jaw to ensure that no gap opens up underneath these parallels even if the movable jaw should lift during the closing operation.

Figures 8 and 9 illustrate a second embodiment of the invention provided with such downward-bias means.

As can be seen in Figures 8 and 9, pot magnets 1 2 provided in the movable jaw element 5b serve to hold a parallel 7 up against the element 5b; in addition, two horizontal rods 15 each pivoted at one end on the jaw block 5a and pulled downwardly by a respective bias spring 16, extend through respective apertures 1 7 in the parallel 7 and serve to exert a downward bias force on the latter. The bias arrangement provided by the rods 1 5 and springs 1 6 ensure that the parallel 7 is kept in constant contact with the table 3.

An alternative form of downward-bias means is illustrated in Figures 10 and 11. In the embodiment of the invention shown in these Figures, the means used to produce the downward bias force are in fact also used to hold the parallel 7 against the movable jaw element 5b, these means being constituted by two tension springs 1 8 secured at one end to the movable jaw block 5a and at their other ends to the parallel 7. The points of attachment of the springs 1 8 to the parallels 7 and jaw block 5a are so selected that the springs apply both horizontal and downward forces to the parallel 7. It will be appreciated that with this arrangement it is not necessary for the parallel to be made of ferrous material as was required with the two previously described embodiments of the invention.

The workpiece mounting arrangements illustrated in Figures 4 to 11 can be used in conjunction with machine tools such as milling machines, jig-boring machines and drilling machines. Furthermore, several such mounting arrangements could be arranged in parallel to enable a number of workpieces to be set up together as is generally the case with n/c machine tools.

Various modifications to the described embodiments of the invention are, of course, possible. Thus, for example, with reference to the embodiment of Figures 4 to 6, the magnets 1 2 could be provided on the parallel 7a, 7bwith the jaw elements 2b, Sb, being made of ferrous material; such an arrangement is not preferred, however, since it unnecessarily complicates the fabrication of the parallels.

Furthermore, since the parallel associated with the fixed jaw of the vice is not subject to the lifting effect experienced by the movable jaw, there is strictly no need to arrange for this parallel to be held against the fixed jaw in a manner enabling its movement relative thereto; it would thus be theoretically possible to rigidly attach the parallel to the fixed jaw.

In practice, this is not desirable as it would involve different holding arrangements for the parallels of the fixed and movable jaws which would lead to increased costs.

Generally, the jaw elements 2b and Sb are attached to their respective jaw blocks 2a, 5a by recessed screws which provide a semipermanent connection between the jaw elements and jaw blocks.

However, in certain applications it would be useful to be able to change one set of jaw elements for another without the time penalty that would normally be involved in unscrewing one set of elements and the screwing on another set. Thus, for example, it may be desired to interchange for a limited machining run a standard set of hardened jaw elements with a set of serrated hardened jaws for holding rough castings, or with a set of soft jaws that can be conformed to the irregular contours of a workpiece. (Another possible reason for wishing to change the existing set of jaw elements is where a ferro-magnetic workpiece is to be machined in a vice of the form shown in Figures 4 to 7 and must be seated so far down in the vice that the magnets 1 2 provided in the jaw elements are not fully covered by the parallels 7. In this situation, machining swarf would be attracted to the magnets increasing the cleaning problem; to avoid this difficulty, it is generally desirable to replace the jaw elements with ones not provided with magnets.

With a view to facilitating the changing of jaw elements, the present invention provides, in another aspect, a vice including a pair of cooperating jaws each comprising a jaw block mounting a corresponding jaw element, at least one of the jaw blocks being displaceable towards the other to enable a workpiece to be gripped between the jaw elements and one or both jaw elements being leleasably coupled to its associated jaw by magnetic coupling means.

Preferably, these magnetic coupling means are constituted by one or more button magnets inserted into the corresponding jaw block, the associated jaw element being made of a ferromagnetic material, at least in part.

Figures 1 2 to 14 show three forms of vice each provided with pot magnets coupling its jaw elements to their associated jaw blocks.

In the form of vice shown in Figure 12, the jaw blocks 2a, 5a have opposed, parallel faces 20 in each of which is embedded one or more pot magnets 21. These magnets 21 serve to hold ferro-magnetic jaw elements 2b, 5b in contact with the jaw faces 20. When it is desired to change the jaw elements 2b, 5b, it is a relatively quick and simple matter to pull the existing jaw elements from the faces 20 and replace them with different elements.

The jaw elements 2b 5b may,of course, themselves be provided with parallelretaining magnets 1 2 in the manner previously described with reference to Figures 4 to 9. It should be noted that it is generally unnecessary for the jaw elements 2b, 5b to be accurately positioned on their associated jaw blocks 2a, 5a so that there is no need to make provision for countering any lifting effect that may be experienced upon the vice being closed on a workpiece (provided, of course, that such lifting is not sufficient to raise the jaw elements into the intended path of the machinery tools).

Tap down of the workpiece to ensure proper seating of the parallels will, in fact, generally also reseat the jaw elements.

Nevertheless, if desired, the jaw blocks 2a, 5a and jaw elements 2b, 5b can be configured as cooperating wedge members as illustrated in Figure 13, whereby as the vice is closed, the jaw elements are forced down against the vice table 3.

Indeed, the jaw elements 2b, Sb may have their ability to move laterally and/or vertically over the jaw block faces 20 either partiaily or totally restrained by suitable mechanical means such as a cooperating projection and aperture arrangement. Thus, for example, Figure 14 shows a jaw element 2b provided with a pin 23 arranged to engage in a vertical slot 24 formed in the jaw block 2a whereby to permit vertical movement of the jaw element 2b over the face 20 while preventing transverse movement.

Although the pot magnets 21 have been shown in Figures 1 2 to 1 4 as provided in the jaw blocks 2a, 5a, it will be appreciated that the magnets 21 could alternatively be embedded in the jaw elements 2b, Sb in which case the jaw blocks would be formed of ferromagnetic material.

Claims (14)

1. A workpiece mounting arrangement comprising: - a vice including a body defining a vice table and a pair of cooperating jaws at least one of which is displaceable towards the other jaw to enable a workpiece to be gripped therebetween; - a pair of parallels for locating the workpiece at a desired height above the vice table; and - force-applying means for releasably holding the parallels against respective ones of the vice jaws, the force-applying means operating in a manner, in respect of the or each displaceable jaw, enabling the associated parallel to be moved over the face of the jaw.

2. A workpiece mounting arrangement according to Claim 1, wherein for the or each displaceable jaw, the force-applying means is arranged to hold the associated parallel against the jaw face with a force sufficient to render the friction therebetween adequate to support the jaw in a lifted state.

3. A workpiece mounting arrangement according to Claim 2, wherein for the or each displaceable jaw, downward-bias means are provided for holding down the associated parallel against any lifting effect experienced upon closure of the jaws.

4. A workpiece mounting arrangement according to any one of the preceding claims, wherein the said force-applying means are constituted by magnets embedded in the face of the vice jaws, the parallels being made of a ferrous metal.

5. A workpiece mounting arrangement according to Claim 4 when dependent on Claim 3, wherein the said downward-bias means are constituted by a spring-biased lever pivoted on the jaw and arranged to engage and apply a downwards force to the associated parallel.

6. A workpiece mounting arrangement according to Claim 3, wherein for the or each displaceable jaw, the force-applying means and the downward-bias means are jointly constituted by one or more tension springs attached at one end to the jaw and inclined upwardly for attachment at their opposite ends to the associated parallel whereby to draw the latter both against the jaw and downwardly.

7. A workpiece mounting arrangement according to any one of the preceding claims, wherein each parallel is composite in form and comprises a narrow primary parallel in contact with the workpiece and a wider, tableprotecting, secondary parallel interposed between the bottoms of the narrow parallels and the vice table.

8. A workpiece mounting arrangement according to Claim 7, wherein the primary and secondary parallels of each composite parallel are separately held against the corresponding jaw by the force-applying means.

9. A workpiece mounting arrangement according to Claim 7 when dependent on Claim 3, wherein the downward-bias means associated with the or each displaceable jaw is arranged to act solely on the narrow primary parallel of the associated composite parallel.

10. A workpiece mounting arrangement according to any one of the preceding claims, wherein the or each displaceable jaw is provided with lateral wipers which serve to wipe away swarf from the regions behind the lateral portions of the associated parallel.

11. A workpiece mounting arrangement according to any one of the preceding claims wherein the vice body provides two lateral wings extending on respective sides of the vice table and upon which the ends of the parallels are arranged to seat.

1 2. A workpiece mounting arrangement substantially as hereinbefore described with reference to Figure 4 to 6, 8 and 9, or 10 and 11 of the accompanying drawings.

1 3. A vice including a pair of cooperating jaws each comprising a jaw block mounting a corresponding jaw element, at least one of the jaw blocks being displaceable towards the other to enable a workpiece to be gripped between the jaw elements, and one or both jaw elements being releasably coupled to its associated jaw by magnetic coupling means.

14. A vice substantially as hereinbefore described with reference to Figures 12, 1 3 or 1 4 of the accompanying drawings.