GB2123721A - Work-clamp pallet for machine tool - Google Patents

Abstract

A work-clamp pallet is described which can be used to facilitate clamping of works on a table (4A) of a machine tool and is aimed at improving the working efficiency of the machine tool through shortening of the time for exchanging works on the table and also at facilitating positioning of the works on the table along both X and Y axes with simultaneous improvement of the ion precision thereof for resultant improvement of the work machining precision. A large number of works are positioned on a work-clamp pallet (3) along the Y-axis by the aid of a standard frame (40) fixedly secured to a base block (20) thereof and also along the X-axis by the aid of positioning stoppers (47) projecting sideways from the standard frame and the works now accurately positioned are then clamped against the standard frame by means of clamping devices (41) disposed opposing at least one side of the standard frame. This preparatory procedure of positioning and clamping a large number of works on the pallet's base block is done outside the machine and, when the machine has stopped with one cycle of machining over, a work-clamp pallet ready is transferred onto the table in exchange for that with finished works on which is withdrawn therefrom. On the table the work- clamp pallet of the invention can be positioned longitudinally as well as laterally with a high precision by the aid of a positioning means (9), the base block thereof is provided with and clamped in place quickly with a high precision, and thus by a single, quick pallet-changing procedure a large number of works can be exchanged on the machine's work table all at once within a very short time. <IMAGE>

Description

SPECIFICATION Work-clamp pallet for machine tool Background of the Invention 111 Field of the Invention The present invention relates to a work-clamp pallet for a machine tool which can be locked on the machine's work table and removed to facilitate quick exchange of works on the table for improvement of the working efficiency of the machine tool.

(2J Description of the Prior Art These years quite remarkable has been the improvement of productivity also of machine tools and with the latest NC (numerically controlled) machine tools such as machining centers, in particular, the working efficiency as well as precision in machining has been improving steadily and rapidly with progressive automatization of operation.

On the other hand, however, the work-changing work still remains time-consuming with little improvement made to date. As a result, the proportion of the time required for changing works to the overall working hours has been steadily and rapidly increasing in sharp contrast to that of actual machining time that has been reduced almost dramatically, and now it is accepted to be a major bottleneck for the desired improvement of working efficiency in machine tool operation.

Meanwhile, the initial costs of machine tools have been increasing remarkably keeping pace with their increasing speed and production capacity.

Such being the case, now increasing recognized is the importance of drastically shortening the time required for changing works on the machine's work table for improvement of the overall working efficiency of machine tools so that their high production capacity can be fully exhibited for desired improvement of their productivity.

Of the prior art, considered useful to meet this desire is, among others, the work-clamp pallet described in U.S. Pat. No.3,899,162. (See FIG. 43.) Its construction is as described below.

On its base block 201 are arranged 5 pairs of hydraulic cylinders 202, each pair thereof opposing each other longitudinally (laterally on the drawing). Amid between the opposing pairs of hydraulic cylinders 202 at a lower level there is provided longitudinally a positioning device 203.

In this positioning device 203 an upwardly tapered block 204 is guided by a pair of vertical guides 205 to be movable only vertically and is urged from under upwardly by a spring 206.

The tip of a piston rod 207 of each hydraulic cylinder 202 has secured to it a positioning block 208 and above it there is fixedly disposed a clamping block 209. The front end face of the positioning block 208 is finished as an inclined face 210 which comes into contact with the tapered block 204.

In the topside of the clamping block 209 is provided a recess 212 for engaging a work 211 therein. The rear wall face of this recess 212 serves as a clamping face 213 and both side walls thereof as right and left positioning faces 214 respectively.

Described below is how it is used and its functions.

First, the base block 201 is placed on the work table of the vertical machine tool and is precisely positioned longitudinally as well as laterally before it is clamped.

Then the work 211 is set in the recesses 212 of each opposing pair of hydraulic cylinders 202. The width of the recess 212 is dimensioned to match that of the work 211, hence the work 211, as it is set in the recesses 212, comes into contact with both right and left positioning faces 214 to be laterally positioned thereby.

Then, when both hydraulic cylinders 202 are simultaneously driven, the work 211 is clamped between the clamping faces 213 of both clamping blocks 209.

The inclined faces 210 of both positioning blocks 208 then come into contact with the tapered block 204 on both sides thereof and are stopped after the tapered block 204 has been forced down against the force of the spring 206.

Thus, the longitudinal position of the work 211 is determined by the tapered block 204 over both inclined faces 210, both positioning blocks 208, both clamping blocks 209 and both clamping faces 213.

This construction, however, has the following defects or shortcomings.

(1) There is no standard for longitudinal as well as lateral positioning on the machine's work table of the base block of the pallet-clamp pallet, this resulting in a poor positioning precision.

Worse, the required positioning procedure is time-consuming and inefficient.

(2) The work-clamp pallet is clamped on the work table of the machine tool as the works thereon are changed.

Hence, the time required for changing works increases with increasing number of works involved and this means an increased off-hours of the machine tool for work-changing and decreased working efficiency thereof.

(3) For precise lateral positioning of works 211, it is necessary to precisely dimension the width of the recess 212 of the clamping block 209 to match that of the work 211 so as to ensure perfect fitting of both.

This means that a clamping block 209 must be made anew each time the width of the work 211 is changed, that is, each time it is necessary to change the clamping block 209 for one whose recess 214 is dimensioned to match the width of a new work and set the new clamping block 209 in exact positional relationship with the positioning block 208.

This means an increased time required for changing clamping block 209, which is added to the already long work-changing time for further lowering of the working efficiency.

Worse, increased are the off-hours of the machine tool with increasing work-changing time, this again meaning deterioration of the machine's working efficiency.

Moreover, it is quite expensive and also troublesome, for a large number of clamping blocks 209 different in the width of the recess 212 have to be made and kept according to the variety in width of the works involved.

(4) At least two units of hydraulic cylinders 202 are required to clamp one work 211, this making the construction of the pallet complicated and being also expensive.

It also means an increased space required for the hydraulic cylinders 202 with the corresponding decrease of the space available for works, hence the number of works that can be placed on the work table of the machine tool is decreased, the required frequency of work-changing is increased and the efficiency of work-changing is affected, these resulting in deterioration of the overall working efficiency of the machine tool.

(5) For positioning the work 211 only longitudinally, the positioning device 203 and the positioning block 208 are required additionally, hence the construction of the work-clamping pallet is unduly complicated, this resulting in a further increase of its manufacturing cost.

Since both positioning device 203 and positioning block 208 are moving parts, there is an increased risk of error in longitudinal positioning of the work 211, this resulting in a lowered precision of longitudinal machining.

This defect is bound to be aggravated with progressive wear of the moving parts, hence there is much to be desired about its durability.

Summary of the Invention A primary object of the present invention is to shorten the time required for changing works on the work table of machine tool to thereby reduce the off-hours of the machine tool for workchanging for marked improvement of the machine's overall working efficiency so that modern machine tools' features of high machining speed, high machining capacity and high productivity are fully exhibited.

For accomplishment thereof, proposed in the present invention is a work-clamp pallet of a construction, wherein a large number of works can be positioned along the X-axis as well as the Y-axis perpendicular thereto with a high precision before they are clamped in place on the workclamp pallet and also the work-clamp pallet itself can be readily and precisely positioned on the work table longitudinally as well as laterally.

The work-clamp pallet of the present invention is composed of a base block, a standard frame and a plurality of clamping devices described below in detail.

The base block is for having works set and clamped thereon, and is provided with a possitioning means for positioning it on the work table longitudinally as well as laterally, a fixing means for clamping it to the said work table and a work clamping face for clamping works to its base block.

Hence, the work-clamp pallet of the invention with its positioning system can be positioned on the work table readily and precisely, longitudinally as well as laterally.

The standard frame is set on the work clamping face of the base block along its X-axis. Of the two sides of this standard frame against the Y-axis right across the X-axis, at least one has defined on it unit work positioning faces at a proper pitch along the X-axis. And at one end along the X-axis of each unit work positioning face there is provided a projecting positioning stopper for positioning the work along the X-axis.

Hence, with this work-clamp pallet, a large number of works can be positioned on the workclamping face of the base block readily and precisely by simply bringing each thereof into contact with each unit work positioning face of the standard frame and the corresponding positioning stopper along the X- as well as Y-axis.

On the work clamping face of the base block each clamping device is disposed across a work accommodating space from each unit work positioning face of the standard frame. Each clamping device is composed of a clamping unit proper, a clamping block and a driving means.

Clamping unit proper is guided by a guiding means to be displaceable on the work clamping face both-way along the Y-axis and is provided also with a fixing means to be fixed in place thereby.

The driving means is supported by the clamping unit proper and drives the clamping block toward or away from the unit work positioning face.

Each work positioned along the X- as well as Y-axis on the work clamping face of the base block can thus be clamped by the clamping block of each clamping device against the corresponding unit positioning face of the standard frame.

The work-clamp pallets of the invention described above may be used as at least two sets for alternate use on the work table of machine tool.

First, on one of the two sets a large number of works are clamped and the loaded work-clamp pallet is transferred onto the work table of machine tool and, after positioning longitudinally as well as laterally by the provided positioning means, which can be done readily and precisely, is clamped to the table by the clamping system also provided. Now the works on the pallet are ready for machining.

Meanwhile, i.e. while the machine tool is at work, another large number of works are positioned and clamped on the other set of workclamp pallet in work changing station for the next cycle of machining.

When machining on the works set on the former work-clamp pallet is over, the other pallet ready with a large number of new parts is transferred onto the work table in exchange for the finished pallet, and is positioned longitudinally as well as laterally quickly and precisely before it is clamped to the table.

Thus, by a single exchange of the said former set for the latter set of work-clamp pallet suffices for the supposedly troublesome work of positioning a large number of works along the X as well as the Y-axis precisely and subsequently clamping them, and the work can be done much quicker this way.

Also, the present invention seeks to simplify the work of positioning works along the X as well as the Y-axis of the work table with increased readiness and improved precision to thereby improve the precision of machining the works as well as the overall machining efficiency.

With the pallet of the present invention, works can be positioned along the X as well as the Y-axis on the base block of the pallet readily with a high precision by simply bringing each of them into contact with both the work positioning face and the positioning stopper. The base block of the pallet itself with its positioning system can be readily and precisely positioned on the work table longitudinally as well as laterally. Hence, by the aid of the work-clamp pallet of the invention with its positioning system, base block, work clamping face and positioning stopper, positioning of a large number of works on the work table can be done readily with a high precision along its X as well as Y-axis.

The present invention furthermore seeks to reduce the space occupied by the work-clamping system to thereby increase the space available for the works on the work clamping face of the base block for increasing the number of works which can be readied for machining at a time, reducing the frequency of work-changing on the base block for the desired improvement of work-changing efficiency, and also for reducing the frequency of changing work-clamp pallets on the work table for the desired improvement of the overall working efficiency of the machine tool.

While in the quoted prior art two sets of hydraulic cylinder are required for clamping a single piece of work, in the pallet construction of the present invention only one set of clamping device, which is equivlent to a hydraulic cylinder, need be used and the standard frame is provided in place of the other set of hydraulic cylinder in the prior art. Compared with the hydraulic cylinder, the standard frame is much simpler in both construction and configuration, also being much more compact, hence sizably reduced is the space occupied by the work-clamping system or equipment with resulting increase of the space on the base block available for works.

The present invention furthermore seeks to reduce the cost of manufacturing the work-clamp pallet by simplifying the construction of the equipment required for clamping works on the base block as well as of the equipment required for positioning works on the work clamping face of the base block along the X as well as the Y-axis so as to make the pallet more compact, at the same time to improve the precision of machining works, to reduce the risk of pallets getting loose due to wear and to improve the durability thereof.

With the pallet of the present invention, the construction as well as configuration of the equipment required for clamping works can be made definitely simpler by the use of the said standard frame instead of said other set of hydraulic cylinder in the quoted prior art, also sizably reduced being the size of the work-clamp pallet.

Also simplified to a large extent is the construction of the equipment required for positioning works on the work-clamping face of the base block along the X as well as Y-axis in the absence of the positioning device with its tapered block, positioning blocks and clamping blocks with the said combined recess of known complexity taught by the prior art, the said equipment composed of only the work positioning face of the standard frame and the positioning stoppers thereon.

Moreover, the said standard frame, work positioning face and positioning stoppers are all stationary components not supposed to move, hence gone is the risk of the precision of machining works being affected by increased clearances between moving parts due to progressive wear, also improved for the same reason being the durability of the work-clamp pallet of the invention.

Further, when the clamping devices are disposed symmetrically on both sides of the standard frame so that the unit work positioning faces on both sides of the standard frame are pushed thereby symmetrically over the works set, the standard frame is required to withstand the resulting simple compression, hence markedly relieved are its loading conditions. Hence, it is possible to sizably reduce its thickness along the Y-axis with resultant increase of the space available for works.

The present invention also seeks to enable clamping works different in width within reason easily and precisely without replacing the clamping block as it was the case with the quoted prior art and without any risk of work-positioning error in the direction of the X-axis, to thereby eliminate the defects of the prior art stemming from the necessity of replacing the clamping block each time when the width of the work is changed, namely prolonging of the work-changing time and the resultant lowering of the work-changing efficiency and even the overall working efficiency of the machine tool, increased cost due to the necessity of making many clamping blocks different in the width of the work-engaging recess and increased care required for keeping them.

With the pallet of the present invention, the work can be positioned only at one end thereof along the X-axis by a single positioning stopper with the other end free, hence precise positioning by the same positioning stopper along the X-axis is feasible even if the work's width, i.e. its dimension along the X-axis, is changed within reason, and the positioned work can be clamped by the same clamping block.

Brief Description of the Drawings FIGS.1~39 relate to embodiments of the present invention, while FIG. 40 is given to show the quoted prior art.

FIGS.1~29 deal with a principal embodiment, while FIGS. 30~42show alternative embodiments relating to the first to 9th alternative embodiments.

FIG. 1 is a plan view of a vertical machine tool and a pallet-changing table of the present invention.

FIG. 2 is a side view of that shown in FIG. 1.

FIG. 3 is a vertical sectional side view partially showing a travelling gear of a work-clamp pallet.

FIG. 4 is a vertical sectional view of an auxiliary table taken along the line lV-lV in FIG. 1.

FIG. 5 is a vertical sectional view of the auxiliary table taken along the line V-V in FIG. 1.

FIG. 6 is a vertical sectional front view showing a part of a clamping device and the travelling gear.

FIG. 7 is a vertical sectional front view showing a part of the travelling gear.

FIG. 8 is a vertical sectional front view of a pallet bed and a guide rail.

FIG. 9 is a vertical sectional front view of a positioning device.

FIG. 10 is a pneumatic/hydraulic system chart of the positioning device and clamping device.

FIG. 11 is a perspective view of the work-clamp pallet and the auxiliary table.

FIG. 1 2 is a plan view of the work-clamp pallet.

FIG. 13 is a front view of the work-clamp pallet.

FIG. 14 is an enlarged vertical sectional side view of essential parts of the work-clamp paliet.

FIG. 15 is a vertical sectional side view of a modified standard frame.

FIG. 1 6 is a vertical sectional front view showing a part of the standard frame in FIG. 15.

FIG. 1 7 is a partial perspective view of the standard frame.

FIG. 18 is a pneumatic/hydraulic system chart of the clamping device and hydraulic pressure supply device of the work-clamp pallet.

FIG. 19 is a vertical sectional side view showing a part of a push-pull means for a clamp frame relating to a modified work-clamp pallet.

FIG. 20 is a partial perspective view of a modified standard frame.

FIG. 21 is a perspective view of a modified positioning stopper.

FIG. 22 is a partial plan view of the work-clamp pallet showing the way it is used with an auxiliary clamping block and/or auxiliary stopper.

FIG. 23 is a partial perspective view of a modified standard frame.

FIG. 24 is a partial plan view of the work-clamp pallet showing the way it is used with a rotation checking plate.

FIG. 25 is a partial vertical sectional side view of the work-clamp pallet showing the way it is used with the auxiliary clamping block.

FIG. 26 is partial plan view of the work-clamp pallet showing the way it is used with a work retainer.

FIG. 27 is a partial perspective view of the work retainer of FIG. 26.

FIG. 28 is a partial vertical sectional side view of essential parts of the work-clamp pallet showing the way it is used with a flat work retainer.

FIG. 29 is a partial front view of a holding plate of the flat work retainer.

FIG.30~32 relate to a first alternative embodiment, of which: FIG. 30 is an enlarged vertical sectional side view of essential parts of the work-clamp pallet.

FIG. 31 is an illustration showing the loading conditions of the standard frame.

FIG. 32 is another illustration showing the loading conditions of the standard frame when it is not backed up.

FIG. 33 is a partial enlarged vertical sectional side view of the clamping device in a second alternative embodiment.

FIG. 34 is a partial enlarged vertical sectional side view of the clamping device in a third alternative embodiment.

FIG. 35 is a partial enlarged vertical sectional side view of the clamping device in a fourth alternative embodiment.

FIGS. 36 and 37 relate to a fifth alternative embodiment, of which: FIG. 36 is a perspective view of the work-clamp pallet of a horizontal machine tool.

FIG. 37 is a front view of that shown in FIG. 36.

FIG. 38 is vertical sectional side view of the clamping device of the work-clamp pallet of fixed type shown in the quoted prior art.

Description of the Preferred Embodiments Referring to FIGS. 1-28, described below is the preferred embodiment of the present invention.

As shown in FIGS. 1 and 2, an NC (numerically controlled) vertical machine tool 1 has provided in front of it a rotary pallet changing table 2 with spaces on it for two work-clamp pallets. The machine tool 1 has fixedly secured on its movable table 4 an auxiliary table 4A for positioning and clamping the work clamp pallet 3 thereon and the work-clamp pallets 3 are exchangeable between the pallet changing table 2 and the auxiliary table 4A.

At a work changing station X on the pallet changing table 2 a large number of works 5 are positioned with a high precision on one of the work-clamp pallets and are clamped in place by a clamping device 41, and then the pallet changing table 2 is rotated horizontally by half a turn (1 80C) to bring the said work-clamp pallet 3 to a workclamp pallet changing station Y.

Then the works Amp pallet 3 is transferred from the work-clamp pallet changing station Y onto the auxiliary table 4A being guided by a guide means 7 and after being stopped thereon by a stopper 8, it is positioned by a pair of positioning devices 9 and then securely clamped on a pallet bed 11 of the auxiliary table 4A by hydraulic clamping means 10.

Thus, by positioning the individual works on the work-clamp pallet 3 and this with respect to the table 4 with a high precision, the individual works 5 can be positioned with respect to the table 4 with an equally high precision as will be described later in greater details.

With the work-clamp pallet 3 thus clamped securely to the auxiliary table 4A, the machine tool 1 is started for machining.

While the machining is under way, works 5 are set on the other work-clamp pallet 3 at the work changing station X.

Upon completion of one cycle of machining, the work-clamp pallet 3 on the auxiliary table 4A is transferred onto the work-clamp pallet changing station Y, and the pallet changing table 2 is again rotated by half a turn (1800) to shift the workclamp pallet 3 with the finished works 5 on to the work changing station X with simultaneous shifting of the work-clamp pallet 3 with unfinished works 5 on to the work exchanging station Y, and the above procedure is repeated for successive exchange of the work-clamp pallets 3.

Now described briefly are the constructions of the pallet changing table 2 and the auxiliary table 4A.

The pallet changing table 2 has arranged on its base frame 2a a rotary frame 26 to be horizontally rotatable on castors 2d with a shaft 2c as the center, and on the top plate of the rotary frame 2b are arranged two travelling rails 12 and one guide rail 7. Reference numeral 2e denotes a stopper, 1 3 a rotation locking means, 14 a rotary shaft and 1 5 an electric motor to be provided as necessary.

The auxiliary table 4A is constructed as a unit with various devices and means arranged on its rectangular baseplate 16, and is secured with bolts 17 on the table 4.

Thus, the top plate 16 have arranged thereon two, left and right, travelling rails 18, a pair of positioning means 9 on both sides thereof and as remote as possible therefrom, clamping means 10 in 6 pairs, 2 pairs each on the left and right sides and at the center, pallet beds 11 disposed on both, left and right, sides of each clamping means 10, guide rails 7 extending before and after each central clamping means 10 and a pair of left and right stoppers 8 etc.

As seen from FIGS.3~9, there are provided as travelling gears 19 from the work-clamp pallet 3 U-sectioned frames 23 each carrying castors 22, which frames 23 are set freely adjustable vertically in square-sectioned grooves 21 formed in the underside of the pallet's base block 20. The said U-sectioned frame 23 is urged downwardly by a compression spring 24 so that the tread part of each castor 22 only is projected beyond the lower edge of the frame 23, which is held by the holders 25 at both ends thereof. (FIGs. 3, 6 and 7).

As shown in FIG. 9, the positioning device 9 consists of an air cylinder and is capable of positioning the pallet's base block 20 with a high precision with a plug 27 being the front end portion of its piston rod 26 fitted into a mating hole 28 in the underside thereof. When the pneumatic pressure is supplied through the working side port 29 for the plug 27 to be fitted into the mating hole 28, the working side port 29 communicates with a detection side port 30 for the pneumatic pressure to be supplied to the detection side port 30 and fitting of the plug 27 (in the mating hole 28) is thereby indicated as will be described below in detail.

As mentioned above, as the work-clamp pallet 3 is shifted from the work-clamp pallet exchange station Y onto the auxiliary table 4A, the guide rails 7 are fitted in the guide groove 31 in the underside of the base block 20 for relative sliding therein and the base block 20 is guided thereby to be free from sideway shifting.Further, each clamp arm 1 Oa does relative movement in the fixing means 32 formed as a T-sectioned groove in the underside of the base block 20 and after positioning of the base block 20 by the positioning device 9, hydraulic oil is supplied to a hydraulic oil chamber 1 Ob of the clamping device 10 for pulling down the clamp arm 1 Oa and with the resulting compression of the compression spring 24 of the travelling device 19 the tread of each castor 22 is retracted to be flush with the underside of the base block 20 and the base block 20 is thereupon clamped on the pallet bed 11.

At this moment compressed air is caused to gush out of air outlets 33 in the topside of each pallet bed 11 to blow off any foreign object on the pallet bed 11 to thereby prevent engagement of foreign objects and at the same time allows confirmation of close contact of the underside of the base block 20 with the topside of the pallet bed 11 through detection for rise of the pneumatic pressure in the said compressed air supply channel 34.

In Fig. 10 is shown the hydraulic/pneumatic circuitry for the devices in/on the said auxiliary table 4A.

Compressed air is supplied from a compressed air source 35 to a pneumatically driven hydraulic pump 36 to generate a hydraulic pressure to be supplied to the clamping device 10 and at the same time the compressed air is led to the positioning device 9 and the air outlets 33 of each pallet bed 11.

It is so arranged that when the plug 27 of the said positioning device 9 is engaged in the mating hole 28, the compressed air is led to the detection-side port 30 for a pneumatic pressure pilot lamp 37 to be lit thereby.

Since the pneumatic pressure in a compressed air supply channel 38 rises when the base block 20 comes into close contact with the pallet bed 11 underneath, the condition is detected by a pressure switch 39 and the resulting signal is transmitted to light the close contact confirmation lamp (not shown).

Now referring to FIGS.11~29, described in detail is the work-clamp pallet.

The work-clamp pallet 3 is intended for the vertical machine tool 1 and is composed of the base block 20, standard frame 40 and a plurality of clamping devices 41.

The base block 20 is an oblong thick steel plate with its lateral sides longer and its topside forming a flat work-clamping face 42.

As shown in FIGS. 11 and 12, the X axis is taken laterally, the Y axis longitudinally and the Z axis vertically with the center of the workclamping face 42 of the base block 20 as the point of origin.

The standard frame 40 is made of a squaresectioned steel bar and is secured to the workclamping face 42 with 9 fixing bolts 53 along the X axis.

This standard frame 40 has its two sides against the Y axis forming each one workpositioning face 44 and parallel to each workpositioning face 44 across a work accommodating space 45 there is provided a clamp frame 41A secured to the work clamping face 42 slidable longitudinally, i.e. along the Y-axis. Each clamp frame 41 A is provided with 9 sets of clamping device spaced at an equal pitch so that each work 5 can be clamped by each clamping block 46 against the work positioning face 44.

In order that a large number of like works 5 can be positioned at an equal pitch on the work clamping face 42 quickly and can be clamped by the clamping devices 41 against the work positioning face 44, each work positioning face 44 is equally divided into 9 sections or unit work positioning faces 44a and at the same time for positioning of each work along the X-axis there is provided a positioning stopper 47 at one end of each unit work positioning face 44a to project beyond the unit work positioning face 44a.

As shown in FIG.17, the said positioning stopper 47 is gate-shaped and removably fitted from above in the stopper accommodating groove 48 in the topside of the standard frame 40 and, if necessary, secured in place, i.e. in the said groove, by means of a screw 49.

As a large number of works 5 are positioned and clamped on the base block 20, positioning of each work 5 along the X as well as the Y-axis can be done efficiently with ease by bringing one side of each work 5 into contact with the corresponding unit work positioning face 44a and at the same time by bringing another side against the X-axis (e.g. the righthand side) thereof into contact with the corresponding positioning stopper 47.

The position of each work 5 along the Z-axis is determined by means of a height adjuster 50 secured to the work clamping face 42 in the work accommodating space 45. (See FIG. 14.) When the work 5 to be clamped is longer than the unit work clamping face 44a, it may be positioned along and extending over a plurality of unit work positioning faces, if necessary, with a proper number of positioning stoppers 47 removed, and may be clamped by the use of the corresponding number of clamping devices 41.

Thus, small works 5 as well as larger and longer ones with their length extending over the entire width of the base block 20 can be accurately positioned and clamped.

When, as mentioned above, the clamp frames 41A are arranged on both sides of and parallel to the standard frame 40 for clamping the works 5 on both sides of the standard frame 40, the standard frame 40 is then subjected to only compressive forces in the direction of the Y-axis, hence its loading conditions are largely eased compared with when the works 5 are clamped only on one side of the standard frame 40.

Hence, the standard frame 40 can then be designed thinner in the direction of the Y-axis and the work-accommodating spaces 45 can thus be increased.

As the work-clamp pallet 3 is used repeatedly, it is possible that works 5 are set by mistake asymmetrically on both sides of the standard frame 40, and to ensure against deformation of twisting of the standard frame 40 even in such a case, it is advisable to have the standard frame 40 secured to the base block as shown in FIG. 14.

For this purpose, a mating recess or groove 52 may be made in the work clamping face 42 along the X-axis for engaging therein the bottom portion 51 of the standard frame 40 which may then be disengageably secured to the base block 20 by means of fixing bolts 53.

When the standard frame 40 is thus disengageably secured to the work clamping face 42, it is also possible to shift the standard frame 40 to either side of the base block 20 for clamping of larger, wider works 5. (See the first alternative embodiment.) When, however, it is intended for clamping of relatively small works 5 only, the standard frame 40 may as well as unremovably secured to the base block 20 by e.g. welding.

When, on the other hand, it is intended for clamping of large and wide works 5 only, the standard frame 40 may be likewise unremovably secured to the base block 20 displaced toward either side thereof. In such a case, however, the standard frame 40 must be designed to be sufficiently solid for, with the clamping devices 41 disposed only on one side of it, it is bound to be subjected to severer loading conditions.

As shown in FIGS. 15 and 16, a standard frame 40a may as well be secured to the work clamping face 42 by means of fixing bolts 53a with its position freely adjustable along the Y-axis.

Referring now to FIGS. 11,12,14, 18 and 19, the clamping device 41 is described in detail.

The clamping device 41 may be of any design if it is capable of clamping each work 5 against the work positioning face 44 of the standard frame 40, and each clamping unit proper may be provided independently, but in this embodiment the clamping units proper of the clamping devices 41 are connected and housed as a single clamp frame 41 A.

In this preferred embodiment each clamp frame 41 A is disposed on the work clamping face 42 on both side of and parallel to the said standard frame 40 along the X-axis across the work accommodating space 45. Since the width of the work accommodating space 45 is to be adjusted according to the size of the work 5, each clamp frame 41A is secured to the work clamping face 42 by means of fixing means 55, 56, 57 with its position freely adjustable along the Y-axis as described below.

As seen from FIG. 12, the work clamping face 42 has provided in it 10 T-sectioned grooves 55 parallel to the Y-axis extending from both front and rear edges thereof to near the standard frame 40 at an equal pitch, these serving as guide means.

Each clamp frame 41A is secured to the work clamping face 42 at the T-sectioned grooves 55 by screwing each fixing bolt 56, the lower end portion thereof, into the mating T-nut 57 disposed in each T-groove 55 to be freely slidable.

For adjustment of the position of the said clamp frame 41 A, the clamp frame 41 A is to be shifted to the desired position manually with the said fixing bolt loosened and, then, the fixing bolts 56 are to be retightened.

For the purpose, as shown in FIG. 19, a longitudinally shifting means may be provided for the clamp frame 41 A, this consisting of a screw rod 58 set through the T-nut 57a so that the latter moves fore and back in the T-groove 55 as the former is turned.

Further, in the case of a large clamp frame 41 A of a large work-clamp pallet 3, a hydraulic cylinder may be used instead of the said screw rod 58 as the longitudinally shifting means for the T-nut 57a or the clamp frame 41 A itself.

The clamping block 46 of each clamping device 41 is disposed opposite to the corresponding unit work positioning face 44a and is driven fore and back by a clamping means 59.

As the clamping means 59 there is provided in this preferred embodiment a single-acting hydraulic cylinder 59a of restitution spring type housed laterally in the clamp frame 41A and to the tip of its piston rod 60a as its output member 60 is connected the clamping block 46.

Preferably this clamping block 46 may be connected to the output member 60 with a universal joint.

For that the back of each clamping block 46 may be formed as a partly spherical contact face 62 and this may be brought into contact with the tip of the piston rod 60a formed as a spherical seat 61 and a connecting bolt 63 may be used to connect them.

To ensure against ingression of chips into a possible gap between the partly spherical contact face 62 and the spherical seat 61, an annular elastic body 64 is inserted between the head of the connecting bolt 63 and the clamping block 46 for urging the latter toward the piston rod 60a.

As said elastic body 64 may preferably be used a rubber "O"-ring, a compression spring or the like.

To ensure against lifting of the work 5 and press it securely against the work clamping face 42, the hydraulic cylinder 59a is set with its axis inclined so that its piston rod 60a is inclined downwardly toward its tip by approx. 4C for a downward component of clamping force to be produced.

When hydraulic oil is let into a forward-stroke oil room 65 of the hydraulic cylinder 59a, the piston 60b is driven toward the clamping direction, and when this oil room 65 is released of hydraulic pressure, the piston 60b is caused to return by the urge of a spring 67 loaded in a return-stroke room 66.

The forward-stroke oil rooms 65 of the individual clamping devices 41 are communicated by the oil channel 68 provided in the clamp frame 41 A therethrough and the hydraulic device 70 described below.

After clamping a plurality of works 5 on the work-clamp pallet 3 placed on the pallet changing table 2, by means of the said hydraulic clamping devices 41, the work-clamp pallet 3 is transferred onto the movable table 4 of the machine tool 1, with the oil channel 68 closed by a shut-off valve 69 at the end of it to disconnect from the hydraulic pressure supply source 70.

As shown in FIG.18, the discharge port 72 of a hydraulic pump 71 of the hydraulic pressure supply device 70 is connectible to the hydraulic oil inlet-outlet port 73 of the work-clamp pallet 3 by means of a hydraulic hose 74.

The said hydraulic oil inlet-outlet port 73 is formed as a joint of self-seal coupling 73A type, and a non-leak reversible shut-off valve 69 is installed in the oil path 68 downstream of the said hydraulic oil inlet-outlet port 73 so that the oil path 68 is switchable between feeding and draining.

This shut-off valve 69 has built in it a check valve so as to be capable of perfectly shutting down the hydraulic oil flow.

The hydraulic pressure supply device 70 reduces the pneumatic pressure from an air source 75 alternatively by one of its three reducing valves 76a, 76b and 76c of different pressure levels and the reduced pneumatic pressure is supplied to the hydraulic pump 71 for a hydraulic pressure (of e.g.

50, 100 or 250 kg/cm2 G) corresponding to the said pneumatic pressure to be generated. This is for properly adjusting the clamping force of the clamping device 41 according to the material, shape and construction of the work 5.

By this it is also possible to first tentatively clamp the works 5 by supplying a relatively low hydraulic pressure to the clamping devices 41 for precise positioning of each work 5, and then to clamp up each work 5 by switching to a higher hydraulic pressure.

A single unit of reducing valve of variable type or a regulator may as well be used instead of the said reducing valves 76a, 76b and 76c.

Then, the self-seal coupling 73A is detached and the work-clamp pallet 3 is transferred onto the auxiliary table 4A to be clamped thereon for machining of the works 5 on the clamped pallet 3.

To ensure against fall of the hydraulic pressure in the hydraulic pressure system of the workclamp pallet 3, there is provided a spring-loaded accumulator 77 in the base block 20 as well as an actuator 78 for detection of any abnormal fall of the hydraulic pressure, and it is so arranged that in the event of any abnormal fall of the hydraulic pressure it is detected by a limit switch 79 on the table 4 side which is triggered thereby.

This arrangement is aimed at precluding fluctuation of the hydraulic pressure by means of the spring-loaded accumulator, which fluctuation is possibly caused by rise or fall of the temperature of the hydraulic oil and the resulting expansion or contraction thereof in the course of time between clamping of the works 5 and completion of the machining thereof.

Besides the said hydraulic oil supply means, there are a number of convenient means that can be adopted.

For instance, it is also possible to provide the work-clamp pallet 3 with a small hydraulic pump and an oil tank of a matching capacity, or alternatively with a small booster. Also it is possible to use a motor-driven hydraulic pump as a component of the hydraulic pressure supply device 70 of the pallet changing table 2 instead of the said pneumatically-driven hydraulic pump.

Further, when the clamping unit proper 41 a of each clamping device 41 is provided independently, it is naturally necessary to supply the hydraulic pressure to each clamping device 41 independently and this inevitably result in a complicated composition of the oil path 68.

Referring to FIGS. 20 N 28, described below in detail are the various jigs used in connection with the present invention.

As seen from FIG. 20, vertical stopper engaging grooves 48a are provided at one end of each unit work positioning face 44a of the standard frame 40b for disengageably engaging a gate-shaped positioning stopper 47a.

As shown in FIGS. 21 and 22, it is possible to attach to each work positioning face 47A of the gate-shaped positioning stopper 47a so as to enable proper adjustment of the position of the work 5 along the X-axis.

As shown in FIG. 23, it is also possible to insert positioning stoppers 47c in mating through holes 48b provided horizontally one above the other in the standard frame 40c on the border between two adjacent unit work positioning faces 44a with end portions thereof projecting with their sides to serve as work positioning faces 47A.

As shown in FIG. 24, it is further possible to insert a rotation checking plate 80 extending over a plurality of clamping blocks 46 between them and the works 5. But for this rotation checking plate 80, the clamping blocks 46 are subject to rotation during machining to cause rotary displacement of the works 5. Such rotary displacement can be perfectly prevented when the said rotation checking plate 80 is used, for, clamped at a plurality of points, it never rotates at the same time checking rotation of the clamping blocks 46.

It is advisable to make this rotation checking plate 80 as a thin metal strip extending over the entire length of each clamp frame 41 A.

As shown in FIGS. 22 and 25, the stroke of the hydraulic cylinder 59a of the clamping device 41 is very limited, hence to make up for it and also to allow use of a larger clamping block 46 according to the size and shape of the work 5 for effective clamping thereof, it is possible to demountably mount an auxiliary clamping block 81 on the clamping block 46 to clamp the work 5 therewith.

In the embodiment shown, this auxiliary clamping block 81 is so designed that it can be easily mounted on the clamping block 46 by loosely inserting the latter in its mating recess 82 and, to ensure against its dropping off, there is provided an effective frictional locking means such as an "0" ring 83.

It is also possible to mount on said auxiliary clamping block 81 another, still larger auxiliary clamping block.

In the embodiment shown in FIGS. 26 and 27, a work retainer 84 for retaining cylindrical works 5 is disposed in each work-accommodating space 45 so as to facilitate setting of cylindrical works 5 in the work accommodating space 85.

When the work retainer 84 is clamped by the clamping device 41, a slit-like deformation compensating gap 86 is reduced for the cylindrical works 5 to be clamped over the retainer 84.

The said work retainer 84 and the work 5 are set on a height adjuster 87 at the desired elevated level.

While it is necessary to change the work retainer 84 when larger works 5 are to be clamped, but when the works 5 to be clamped are smaller, each work 5 may be set in a hollow cylinder of the corresponding size (not shown) before it is set in the work retainer 84 to be clamped over it.

As shown in FIGS. 28 and 29, thin, flat works 5 are to be clamped by the use of a flat work retainer 88.

It is so designed that the work 5 is set on supporting faces 89 with its sides retained by retaining ends 90, one of which is held by the standard frame 40 and the other is pushed by the clamping block 46 of the clamping device 41. The work 5 is clamped securely as one retaining block 90 is driven toward the other and at the same time the work 5 is pushed downward lest it should be lifted by the downward component of the clamping force produced.

A space 92 provided under the work 5 is preferred for it enables boring through the work 5, also serving as chip collecting space.

The retaining block 91, whose upper end portion is the abovementioned retaining end, is formed continuous in the lower part and spaced in the upper part thereof so as to be better adaptable to various works 5.

Described below are a number of partial modifications of the preferred embodiment described above.

I. FIGS. 30 ~ 3232 show a first modification.

When a large work 5 is to be clamped, the standard frame 40 is displaced longitudinally (along the Y-axis), for instance, toward the rear edge of the work clamping face 42 of the base block 20, and the clamp frame 41 A on the front side is set across an increased work accommodating space 45 from the standard frame 40, while the clamp frame 41 A on the rear side is set close by the standard frame 40 without any work accommodating space 45 in between, both secured in place to the work clamping face 42. The clamping blocks 46 projecting out of the clamp frame 41 A are then brought into contact with the opposing unit work positioning faces 44A of the standard frame 40 so that it is securely backed up against the clamping force applied to the work 5.

The works 5 arranged in front of the standard frame 40, these are then clamped by the clamping devices 41 in the front clamp frame 41 A with the unit work positioning faces 44a of the standard frame 40 held by the rear row of the clamping devices 41 are mentioned above.

Since in this modification the standard frame 40 is backed up by the clamping device 41 in the rear row, it is symmetrically compressed from both front and back sides so that its deformation in the direction of the Y-axis is prevented and the position of the standard frame 40 with respect to the coordinate system for the work clamping face 42 is properly maintained. (See FIG. 31.) If the standard frame 40 is not backed up by the clamping devices 41 in the rear row as shown in FIG. 32, the standard frame 40, too, is deformed rearward and with resultant change of the position of each work 5 in the said coordinate system the machining precision of the work 5 is affected.

II. FIG. 33 is given to show a second modification.

In this modification the clamping means 59 of the clamping device 41 consists of a single-acting hydraulic cylinder of spring restitution type 59b, a clamping member 46a is set through a mating bore of a piston 60c as its output member and a manipulating means 60d is provided at the outer end of the clamping member 46a.

The piston 60c is urged by a compression spring 67a loaded in a return-stroke room 66a toward the clamp relieving side and is restrained by the spring 67a lest it should rotate.

When the work 5 is to be clamped on the workclamp pallet 3, it is so designed that the manipulating means 60d is manipulated manually for tentatively clamping and positioning the work 5 and then hydraulic oil is introduced into the forward stroke oil room 65a for clamping up by the hydraulic pressure.

The clamping device 41 in this modification is capable of clamping wide as well as narrow works 5 freely, also featuring a very small stroke of the hydraulic cylinder 59b.

The said clamping means 59 can as well be used as a clamping means consisting of a screwtype clamping member 46a without supplying hydraulic oil to the hydraulic cylinder 59b. In that case, however, more powerful restraining of the piston 60c against rotation is required.

Ill. A third modification is shown in FIG. 34.

In this modification a piston 60e of the clamping means 59 of the clamping device 41 is urged toward the clamping side by a coned compression disc spring 93 set in a forward stroke oil room 65b of a double-acting hydraulic cylinder 59c.

The spring force of the said coned compression disc spring 93 is made as strong as, for instance, 500 1 1,000 kgf so that this spring force can be used for tentative clamping of the work 5 and together with the hydraulic force also for clamping up of the work 5.

So, when the works 5 are to be set at the work changing station X on the pallet changing table 2, it is possible in this modification to bring the clamping block 46 into contact with the work 5, with the hydraulic pressure supplied to the return stroke oil room 66b to cause the piston 60e to retract, and then disconnect the work-clamp pallet 3 from the said hydraulic pressure supply device 70 to release the hydraulic pressure for tentative clamping of the work 5 to be made by the force of the coned disc spring 93.

After proper positioning of the work 5 in said state of tentative clamping, the work-clamp pallet 3 is transferred onto the auxiliary table 4A of the machine tool 1 to be clamped thereon. Then the hydraulic hose from the hydraulic pressure supply device (not shown) on the machine tool 1 side is connected to the hydraulic oil inlet/outlet port (which communicates with the forward stroke oil room 65b of the hydraulic cylinder 59c) and a hydraulic pressure of e.g. 250 kg/cm2 G is supplied to the forward stroke oil room 65b of the hydraulic cylinder 59c for clamping up of the work 5.

It is then also possible to properly set the clamping force in the said procedure of tentative clamping through adjustment of the hydraulic pressure supplied to the return stroke oil room 66b.

When said clamping device 41 is used, the work-clamp pallet 3 can be transferred with the hydraulic hose disconnected without providing it with the said non-leak shut-off valve of reversible type 69 (FIG.18) and, moreover, since it is reconnected to the hydraulic pressure supply device after it has been clamped on the auxiliary table 4A, there is no risk of any trouble such as hydraulic pressure leakage or abnormal fall of hydraulic pressure.

IV. FIG. 35 shows a fourth modification.

The clamping device 41 in this modification uses spring force along for clamping and hydraulic force for unclamping.

For that a powerful coned compression disc spring 93a is set in a forward stroke room 65c of a hydraulic cylinder 59d of the clamping means 59 to urge a piston 60f toward the clamping side.

When works 5 are set at the work changing station X, the clamping blocks 46 are applied to the works 5 with hydraulic pressure supplied to a return stroke oil room 66c to compress the coned disc spring 93a as in the case of the third modification above, and then the hydraulic pressure is released for the works 5 to be powerfully clamped by the force of the coned disc spring 93a. Then, the work-clamp pallet 3 is transferred onto the auxiliary table 4A of the machine tool 1 and clamped thereon for the works 5 to be now ready for machining in the total absence of hydraulic pressure.

IV. A fifth modification is shown in FIGS. 36 and 37.

A work-clamp pallet 3A in this modification is a box-shaped one intended for horizontal machine tools. Its base block 20a is a box-like rectangular parallelepiped body made of steel with work clamping faces 42a formed on the four sides thereof.

With the center of each work clamping face 42a as the point of origin the X, Y and Z axes are set as illustrated. On each work clamping face 42a there is secured a standard frame 40e along the X-axis with its position freely adjustable in the direction of Y-axis and on both sides thereof and parallel thereto one upper and one lower clamp frame 41 D are secured with their positions again freely adjustable.

Each clamp frame 41 D has provided therein 4 sets of hydraulic clamping device 41, each with a clamping block 46 for clamping the work 5 against the corresponding unit work positioning face 44a.

With the standard frame 40e and the clamp frames 41 D all removed, larger works can be clamped by screwing bolts etc. into T-nuts disposed in a T-sectioned groove 55a.

Claims (28)

1. A work-clamp pallet for a machine tool composed of a base block, standard frame and a plurality of clamping devices wherein: the base block is for having one or more works clamped thereon and has arranged therein or thereon positioning means for positioning thereof longitudinally and laterally with respect to a table of said machine tool, a fixing means for clamping said base block on said table and a work clamping face by which to clamp the work or works, the standard frame is clamped on said work clamping face of said base block along its X-axis and unit work positioning face is formed at proper pitch at least one of its two sides against the Y-axis right across said X-axis, and one end of each thereof is defined by a positioning stopper projecting to position each work along the X-axis, each clamping device is disposed on said work clamping face of said base block across a work accommodating space from each unit work positioning face of said standard frame and said each clamping device is composed of a clamping unit proper guided by a guide means to make its position adjustable in either direction along said Y-axis and fixed in place by a fixing means, a clamping block disposed so as to oppose said unit work positioning face of said standard frame and a clamping means installed on said clamping unit proper so as to be able to drive said clamping block toward and away from said unit work positioning face.

2. A work-clamp pallet as recited in claim 1, wherein said base block is a work-clamp pallet intended for a vertical machine tool, is formed of a rectangular thick steel plate and has a work clamping face formed thereon.

3. A work-clamp pallet as recited in claim 1, wherein said base block is a work-clamp pallet intended for a horizontal machine tool, is made of steel as a box-like rectangular parallelepiped body and has one or more work clamping faces on its front, rear, left and or right sides.

4. A work-clamp pallet as recited in any preceding claim, wherein a plurality of said unit work positioning faces are formed at a proper pitch along said X-axis on each of both sides of said standard frame and each clamping device is disposed opposing each unit work positioning face on both sides of said standard frame.

5. A work-clamp pallet as recited in claim 4, wherein each clamping device is disposed close by each unit work positioning face on one side of said standard frame without said work accommodating space in between and said each unit work positioning face is directly backed up by said clamping block of each clamping device.

6. A work-clamp pallet as recited in any preceding claim, wherein said fixing means of said base block is composed of a plurality of T-sectioned grooves along said X-axis provided in the underside thereof.

7. A work-clamp pallet as recited in any preceding claim, wherein a travelling means for transferring said base block onto said table of said machine tool is composed of a plurality of castors installed on the underside of said base block.

8. A work-clamp pallet as recited in any preceding claim, wherein an engaging means extending along the X-axis if provided at the root of said standard frame, and it is engaged with a mating groove extending along the X-axis provided on said work clamping face of said base block to prevent deformation of said standard frame in the direction of the Y-axis.

9. A work-clamp pallet as recited in any preceding claim, wherein said standard frame is removably secured to said work clamping face with its position adjustable.

10. A work-clamp pallet as recited in any preceding claim, wherein said each unit work positioning face is defined at an equal pitch along the X-axis.

11. A work-clamp pallet as recited in any preceding claim, wherein said positioning stoppers are detachably attached to said standard frame.

12. A work-clamp pallet as recited in claim 11, wherein an auxiliary stopper is attached to a workpositioning face of each positioning stopper for position adjustment of said work.

13. A work-clamp pallet as recited in claim 11 or 12, wherein said positioning stopper is disengageably engaged from above in a stopper engageing groove provided in the topside of said standard frame,

14. A work-clamp pallet as recited in any preceding claim, wherein all of clamping units proper of plural clamping devices disposed on one side of said standard frame are linked as a unit.

15. A work-clamp pallet as recited in any one of claims 1 to 13, wherein said clamping unit proper of each clamping device is formed as an independent unit.

16. A work-clamp pallet as recited in claim 14, wherein a push-pull means for displacing said clamping unit proper forward and back along the X-axis is provided between said clamping unit proper and said base block.

17. A work-clamp pallet as recited in any preceding claim, wherein an output member of said clamping means of said clamping device is drivable forward and back along the Y-axis and has a clamping block connected thereto.

18. A work-clamp pallet as recited in any preceding claim, wherein an output member of said clamping means of said clamping device is drivable both ways along the Z-axis right across the X-Y plane, such motion being converted by a mechanism consisting of an inclined cam face of said clamping unit proper and a mating inclined driven face of said clamping block into forward and backward movement of said clamping block.

19. A work-clamp pallet as recited in any preceding claim, wherein said driving means of said clamping device is a hydraulic cylinder.

20. A work-clamp pallet as recited in any one of claims 1 to 18, wherein said driving means of said clamping device is a spring.

21. A work-clamp pallet as recited in claim 1, wherein said driving means of said clamping device is a screw.

22. A work-clamp pallet as recited in any one of claims 1 to 18, wherein said driving means of said clamping device is a single-acting hydraulic cylinder of spring restitution type.

23. A work-clamp as recited in any one of claims 1 to 18, wherein said driving means of said clamping devices is a double-acting hydraulic cylinder-with-spring having a compression spring set in its forward stroke oil room.

24. A work-clamp pallet as recited in claim 1 9, wherein said output member of said driving means has said clamping block screwed therethrough, which clamping block is provided with a manipulating means.

25. A work-clamp pallet as recited in claim 17, wherein said clamping block has a partially spherical contact face which is brought into contact with a mating spherical seat of said output member so as to be able to oscillate said clamping block.

26. A work-clamp pallet as recited in claim 17, wherein an auxiliary clamping block is demountably attached on said clamping block.

27. A work-clamp pallet as recited in claim 17, wherein the longitudinal axis of said output member of said driving means is inclined downwardly toward its front end with respect to said work clamping face.

28. A work-clamp pallet substantially as hereinbefore described with reference to the accompanying drawings and as illustrated in Figures 1 to 39 of the accompanying drawings.