GB2198668A

GB2198668A - Vice

Info

Publication number: GB2198668A
Application number: GB08629731A
Authority: GB
Inventors: Tai-Her Yang
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-12-12
Filing date: 1986-12-12
Publication date: 1988-06-22
Also published as: GB8629731D0

Abstract

An electrically operated clamping device comprising a vice having a guide screw (1) powered by a reversible electric motor (3), together with a drive circuit (801,802) for the motor is characterised in that the motor and drive circuit are such that the torque developed by the motor at the beginning reverse release action is greater than that developed during forward clamping action. <IMAGE>

Description

Improved Electro Clamping Vise ABSTRACT OF THE INVENTION: It is the feature of a structural design of the electro clamping vise that driving motor and transmission gear set (or other speed-reducing equipment) are installed on the srew rod, so that the driving motor can drive guide screw to make positive or reversal rotation by means of the gear set for driving the movable jowl forth and back ater the reduction of the speed; This design can provide an electro driving structural design, in which it can accept the quick motion for clamping the working piece by means of manual or program control or other electro controlling equipment.

Its main structure contains driving motor, guide screw rod and speed-reducing equipment. The output end of the driving motor can couple with big gear or turbine on the guide screw rod by means of the output end of the speed-reducing structure, and the big gear or turbine is used for driving the guide screw rod, so that the guide screw rod can couple with relative motive jowl to make shaft-directional displa- cement.

To adjust the clamping force iTh tis design, the use driving electric circu t and -- motor ca:. oe adjusted on the torsional force or set ted as automatic cut out or conducted by the electric circuit forever for pushing the working piece. In order to make the driving motor more reliable back driving torque for making reliability during the loosing, the driving electric circuit has the control function for increasing the torgue at the twinkling of an eye to move back. Using the said design, the clamping vise with high costs, high noise of air pressure or oil pressure drive.

BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 is a cubic disamounted view of the arrangement of the guide screw rod paralleled to the drivng motor of the electro clamping vise in the present invention.

Fig. 2 is a sectional view of the parallel guide screw rod of the driving motor in the present invention.

Fig. 3 is a A-A sectional view of Fig. 2, Fig. 4 is a cubic mounted view of the arrange met of the guide screw rod paralleled to the driving motor of the electro clamping vi se in the Lreser invention.

Fig. 5 is acubic dismunted view of the vertical guide screw rod arrangement of the driving motor of the clamping vise in the present invention.

Fig. 6 is a sectional view of the vertical guide screw rod of the driving motor in the present invention.

Fig. 7 is a B-B sectional view of Fig. 5.

Fig. 7A is a view of the applicable example of the present invention used in the clamping vise drive of the guide rod in positioning type.

Fig. 8 is a diagramm of the driving electric circuit in positive and reversal drive of the drving motor.

Fig. 8-1 is a driving electric circuit of the series motor in the diagram of Fig. 8.

Fig. 8-2 is a view of the applicable example of the driving electric circuit of AC single phase induction motor in the Diagram of Fig. 8.

Fig. 9 is a view of the applicable example of the driving electric circuit for the driving motor used for making positive and reversal motion.

Fig. 9-1 is a view of the applicable example of the driving electric circuit of the serIes motor in the Diagram of Fig. 9.

Fig. 9-2 is a view of the applicable example of the AC single phase induction motor used as driving motor in the Diagram of Fig. 9.

Fig. 9-3 is a view of the applicable example of the AC three-phase induction motor used as driving motor in the diagram of Fig. 9.

Fig. 10 is a diagram of the electric circuit used for controlling positive and reversal rotation and for adjusting clamping torque.

Fig. 11 is a view of the applicable example of the electric circuit used for controlling positive and reversal rotation with larger reversal back torque.

Fig. 11-1 is a view of second applicable example of the electric circuit used for controlling positive and reversal rotation with larger reversal back torque.

Fig. 11-2 is a view of third applicable example of the electric circuit used for controlling positive and reversal rotation with larger reversal back torque.

Fig. 11-3 is view of fourth applicable example of the electric circuit used for controlling positive and reversal rota ion with larger reversal back toggle.

Fig. 11-4 is a view of the applicable example of Fig. 11-3 used for AC single, split phase motor in the present invention.

Fig. 12 is a view of the applicable example of the carbon brush set used for generating different reactions, in which the brush is located slopy with the central line.

DETAILED DESCRIPTION OF THE INVENTION: The conventional clamping vise and vise clamp the working piece by means of rotation of the guide screw rod with the hands. The clamping vises located on the table or on the working table are used for repeate works, when they are used in the operation.

At this moment, the conventional hand vise can reduce the working efficiency. Although there are oil pressure or cylindrical driving products in the market, but they generate high noise and has the polution characterics.

The present invention provides a driving structure with small volume, economic and healthy one which can quickly drive the movable jowl. Using the manual or program control or other electro controlling equipment for driving an controlling the current sign anc for selecting the motor, the following working types can be provide: I. When the clamping vise clamps the working piece, the driving motor reduces the speed first and then drives the guide screw rod for driving quickly the movable jowl near to the working piece.Using the working piece near to working piece, the motor driving controlling equipment used for controlling the electric current cuts of automatically the electric source, when the loading current increases; At the present, the driving stops or it gives only limited electric current for keeping the motor a constant torque. It is the feature of the said driving equipemnt which can control the electric current that the torque in the reversal rotation is equal to or greater than the torque in positive rotation, so that the be motion of the clamping vise can be sured.

II. The last action can be made by hand for rotating the guide screw rod or for clamping main shaft of the driving motor, and the travel is adjusted by the motor.

This design needs small horse power, and the controiling equipment must only provide the motor positive and reversal rotation. It needs lower cost.

Now we describe the detailed description of the present invention based on the enclosed drawings as follows: As shown in Fig. 1, the driving motor is installed on drive seat 2 of guide screw rod 1, in which it contains a st cf driving motor 3 with speed-reducin gear case, a set of big and small gears 41, 42 which are coupled each other, and a driving seat 2 with s-'::table space as w-tl as a ccnnect -. cover 5, whereto A key groove 11 is installed on the rod side of guide screw rod 1 in the direction of the shaft, and is coupled and penetrated with the screw hole 21 of driving seat 2, The end of the rod has square head for encasing the hand handle to make a rotation with the hand; Driving seat 2 and bottom seat 6 are made in one piece, and a screw hole 21 is installed facing to the guide screw rod 1, in which the groove holes are located in the inner side and used for positioning the bearing in the shaft direction.

A hole seat is installed just under the back screw hole 21 for extending and positioning the speedreducing gear case of driving motor 3, and the output shaft of speed-reducing gear extends to driing seat 2 for driving the small gear 42; The speed-reducing gear case is installed at the front end of driving motor 3; During the assembly, the speed-reducing gear case incling driving motor itself 3 can be buried in the groove holes of driving motor 2.The driving seat is leant by the transverse convex plate extending from the speed-reducing gear and is fixed by the fixing ice, as shown in Fig. 2 & 4; Big and small gear set 41, 42 are used for transfering the force of driving motor 3 to guide screw rod 1, in which small gear is installed on the output shaft of speed-reducing gear case, and big gear 41 is installed penetratedly on the guide screw rod 1 for coupling small gear 42; The said big gear 41 drives the guide screw rod 1 by means of the key 411.

As shown in Fig. 2, 3 & 4, the connecting cover 5 is made as convex part upward in the middle on the basis of matching the configuration of the driving seat 2, and its two sides are made as flat plates, in which the convex part is used for leaning closely on the driving seat 2, and its two sides are locked on the bottom seat 6. As shown in Fig. 2, before the connecting cover 5 has been positioned, the big gear is penetrated at first and the small gear 42 is then penetrated.

At the same time, two shaft-directional bearings are installed on two sides of big gear 41, and a shaft-directional bearing is installed on the front side of small gear 42 to make all transmission elements exact positioning. Moreover, a convex shaft 31 with square handle is installed on the back side of the driving motor for manaul operation of the handle, as shown in Fig. 4.

Through the controlling of the switch, the driving motor 3 drives smell gear 42 through speed-reducing gear, and then through big gear 41 to drive guide screw rod by way of key 41 , Sc that the quick feeding and back motion are achieved.

Moreover, this stop control can be further achieved by the preseted push button, or the AC or DC motor can be driven by the selectable motor ( such as series motor, in which the load current and stopping current has less difference and the motor has larger magnetic winding) or the DC/AC driving motor is driven by limited power supply.

Similarily, the front section of fedding drive of guide screw rod 1 can be driven quickly by the driving motor 3, or the motor is pulled to separate the gear 42 from gear 41; Its last section is locked by the square post at end of guide screw rod 1 coupled by the hand handle, or the convex shaft on the back side is driven manually for last locking.

The driving structure of the said electro claim ping vise can be further transverse driving motor 3, and the guide screw rod 1 is driven by turbine rod 420, turbine wheel 420. Its structure is shown as Fig. 5, 6 & 7.

The shaft-directional key groove 11 is installed on the guide screw rod 1 and is coupled with the screw hole 201 of the driving seat 11.

A screw hole 201 is also installed at the penetrated position of guide screw rod î located relwtive to driving seat 20.

Its inner side has two stepped groove holes used for positioning turbine wheel 410 and shaftdirectional bearing. Another two-stepped hole is installed transversely at lower end of side of the said driving seat 20 for penetrating driving motor 3 and turbine rod 420.

A speed-reducing gear case is installed at the front end of driving motor 3, and turbine rod 420 is installed at output end of gear case. During the assembly, it is locked in the double stepped groove hole on the side of driving seat 20 by the positioning plate extending from driving motor 3.

A convex shaft 33 of the hand wheel 32 is installed on convex back side of the motor for manual drive, as shown in Fig. 6, 7.

The turbine wheel 410 penetrated an ccuples in key groove 11 of guide screw rod 1 by means of a key; The circumference of its lower end connects with turbine rod to form a transmission structure.

The shaft-directional bearings are installed on its two sides respectively.

The connecting cover 50 is installed on inner side of the driving seat 20 for pressing shaftdirectional bearing, so that the turbine wheel 410 can be exactly positioned at the position of coupling turbine rod 920.

The said transverse driving motor 3 can drive guide screw rod 1 through turbine rod 420, turbine wheel 410 based on the output dynamic force because of speed reduction, in which the main shaft 31 of the said driving motor 3 can extend from the motor housing. Fig. 7A is a view of the applicable example of the clamping vise, in which the driving structure as-shown in Fig. 1-7 is used for guide positioning type. Its diference from the structure as shown in Fig. 1-7 is that a screw hole 202 is installed on the bottom of movable jowl for penetrating guide rod, and then it is driven and coupled by the dri= ving motor with the gear set, so that it needs no shaft-directional sliding between it and the guide screw rod and it connects with the other based on transmission; There is no.screw hole on the driving seat. There is only penetrating hole used for penetration. It is similar to the conventicnal one, in whcih the end of the guide rod is small for putting stop bearing and for accepting reverse action. it has a section of the screw threads for putting encase ring, positioning screw nut; The big gear is coupled with the guide screw rod and is not accepting and clamping reverse action. Another structure and function are the same as which shown in Fig. 1-7.

In the practic--l application, the said driving clamping structureshave the follof,Sing features: a. It can control Positive and reverse rc.tatitn.

b. It can control positive and reverse rotation and adjust the clamping torque and cut out automatically.

c. It can control positive and reverse rotation and adjust the clamping torque and has the function of continous clamping pressure.

d. During the reverse rotation as shown in points b 8 c, it needs larger torque for overcoming static friction and for ensuring the loosing.

In order to comple with the said requirement, it can be achieved by selecting the motor and the electric circuit of the driving control. The various applicable examples are shown as follows: Fig. 8 shows the circuit diagram of the function shown in point a, in which 801 is a power suppl equipment and can be DC or AC depending upon the kino of the motor;and 802 is a switch of positive and reverse operation and stop. It can be the pus button with manual operative electric machine type or rotary switch. It operated directly durong small power, and it complies with electrric machine type electrmagnetic switch or with electronic solid switch for controlling; 803 is a DC or AC driving rotor and can rare positively or reversely.

There are many electrical engineering technices for selecticr. The applicable earpes of rig. 8 8-2 are as follows As sown in Fig. 8-1, armature A811 and magnetic field form a universal motor used for AC and DC. SW8ll is a positive and reverse threepositional switch. Using it to control the motor, it can rotate positively or reversely or stop. As shown in Fig. 8-2, M822 is a split induction motor in type of AC capacitor constant driving and has starting winding WS821, driving winding WR821 and split phase capacitor C821. It can rotate positively or reversely or stop by means of controlling switch SW821.

As shown in Fig. 9, P901 is a power source which can control AC or DC electric current. It contains the control with automatic cut out of electric current.

Its action can be thermic bimetall type or comparative electric circuit type, and the current-limited type can be series crystal or phase gate fluid or power transformer; 902 is operating switch which can rotate positively and reversely, and which can accept manual or program control or another operation of electric current sign. It can drive directly the motor for rotating positively or reversely or indirect driving electric machine type or electromagnetic switch or electronic solid relay for con tolling the motor to drive positively or reversely or to stop; 903 is a motor used for AC or DC and for positive or reverse rotation and it conncts with current controlling torque.

Fiv. 9-1 is its applicable example, in ic P9il is a over source having the control function of electric current. It is its control function that it cuts out during the overload; Sw911 can be used for driving series motor to make positive or reverse rotation; F911 is a series motor magnetic field; A911 is an amature of series motor.

Fig. 9-2 is a view of the applicable example, in which AC capacitor drives forever the motor.

P921 is a power supply equipment controlling the electric current; Switch SW921 is used for changing over the positive or reverse rotation or stop of the motor; WS921 is a motor start winding; C921 is a-split phase capacitor; WR921 is a driving coils.

Fig. 9-3 is an applicable example, in which the three phase induction driving motor can make Y-wiring advance clarrping drive and filta-wirins back loosing drive. Using a set of progra current sign or manual operating electromagnetic switch. (or 22nd switch), the electric circuit can be controlled in Y-positive rotation or delta-reverse rotation.

During Y-wiring advance, because Y-wiring rectance increases three times, the Y-wiring stop current can be selected as three times of Y-operating current.

Therefrom, the winding can not be burnt during he stopage for generating continous clasping ue. Delta-bac. potion provides a large, back torque for loosing the movable jowl.Moreover, ting switch is installed at the end of bac cruel for safe positioning and stop. The touch position of this switch and movable jowl can be changed by moving switch position or by adjusting the touch block of the movable jowl, so that it can provide a best economic back displacement during the mass production) Fig. 9-3 is a view of the applicable example of manual operating electromagnetic switch, in which M901 is a Y- or Deltawiring three phase AC induction motor; MS-Delta is a back Delta-wiring electromagnetic switch; PB-Delta is its operating push button; MSY is an electromagnetic switch of the driving clamping;PBY is its operating push button; PB901 is a stop push button for cutting out the electric source during all states; LS901 is a back limited switch for cutting out MS-Delta, when the movable jowl moves back; TH5W901 is a thermic switch for-protecting the motor from the overload.

Fig. 10 is a circuit diagram of the driving function as shown in point c, in which P1001 is a power supply equipment with limiting largest current function; 1002 can accept manual or program control or other electric control sign for controlling the motor to make positive or reverse rota ion or stop; lug03 is a driving motor which can rotate positively or reversely.If the said power supply equipment PlOOl when limited largest output current replaces the power supply equipment with automatic cutting function during t-- overload, i.e. part 901 as shown in Fig. 9-1 & 9-2, nen the function of continuous clamping can be 5grieves As known by people, after the guide screw rod during the continuous motion has clamped a working piece, the static friction of transmission therefore increases. At the present, if it is driven back with same torque, it will be not available. In the present invetion, a larger back driving has been designed.As shown in Fig. 11, a power source P1701 with limit of largest output current is used for driving AC spli phase motor with different positive and reverse torques, in whcih C1101 is a split phase capacitor; 111101 is first winding; a.1102 is the second winding with differet winding strength fro Wl 101; When the operating switch position is located at different operating position, the said split phase motor will rotate in different direction and will make the driving with different torque. Its largest torque is which used for driving back the movable jowl.

Fig. 11-1 is a view of the second applicable example, in which in the positive and reverse rotating switch circuit of a driving motor, the positive and reverse rotating switch Sol'1102 is connected with damping rectance in series, when the motor drive positively the movable jowl, (including fixed or adjustable resistance, electric induction or capacitor...etc.) for limiting its torsion force less than the torsion force in back loosing. In the figure, the ,mctcr is a capacitor split phase driving single phase AC induction motor with a positive rotating input and reverse rotating input point, and the power source is a current source P1101 with limiting largest output current.

As shown in Fig. 11-2, Using positive and reverse rotating driving circuit, the positive driving clamping is connected with damping rectance in series for driving positive and reverse rotating DC motor, in which the switch So1103 uses its amature to limit its torsion force less than the torsion force during back loosing through its connected damping element Z1101 in series, when the motor drives in positive direction the movable jowl.

Fig. 11-3 is a view of the limiting circuit 1104, in which the power source has double pressure feeding and is connected in series with the output current; Switch SW1104 is used for selecting the power source voltage and the rotating direction of the motor; It is a view of the applicable example of DC series motor. Using the change-over of three positional switch, the DC motor is driven with positive clamping having less torque and with back reverse rotation having larger torque.

Fig. 11-4 is a view of the applicable example of split phase driving motor with change-over single capacitor, in which the input voltage of operating winding Wr during the positive driving is less than the input voltage during the reverse rotation. Therefore, the torque of positive rota ion is also less than the torque of reverse rotaion.

As shown in Fig. 12, the different torques in positive and reverse rotation of the DC motor can be also achieved by the change-over angle of the electric brush sloping with the changeover central line, based on the fact that different amature reactions during the positive and reverse rotations can generate the different torques.

Moreover, it can be also achieved by the wiring of double magnetization or by the differntial double magnetization. There are many methods to chieve the said gone. The said applicable examples for controlling and driving the motor can certify that the functions of points a, b, c, d are practically available.

Based on the said description, this invention is practical and has simple structure, low noise and low pollution. Please examine it!

Claims

CLAIMS:

1. A structural desing of electro clamping vise, wherein the driving motor and transmission gear set (or other speed-reducing equipment) are installed on the driving seat of the screw rod, so that the motor can drive guide screw rod to make positive and reverse rotaions by means of gear set after it has reduces its speed for driving the movable jowl back and forth; The present invention can provide a electric driving structure for quick clamping the working piece based on aception of manual or program control or other electric control sign; It contains mainly the driving motor, guide screw rod, speed-reducing euqipment and positive and'reverse rotating circuit.

Using the driving control and the selection of the motor, the following working types can be proveded: I. When the clamping vise clamps the working piece, the driving motor reduces the speed at first, and drives the guide screw rod for driving quickly the movable jowl near to working piece.

When the working piece located near to work, the motor driving control equipment used for controlling the electric current cuts out auto magically the power source during increas-e of load current; At this moment, the driving function stops or it gives only a electric current for keeping the motor a constant torque. It is the feature of the said driving equipment which can control the electric current that the torque in the reverse rotation is equl to or greater than the torque in positive rotation, so that the back movement of the clamping vise can be ensured.

II. The last action can be made by hand for rotating the guide screw rod or for clamping the main shaft of the driving motor, and the travel is adjusted by the motor.

2. A driving clamping structure as described in claim 1 has the following features: a. It can control positive and reverse rotation.

c. It can control positive and reverse rotation and adjust the clamping torque and has the function of the continuous clamping pressure.

d. During the reverse rotation as shown in points b and c, it needs larger torque for overcoming the static friction and for ensuring the loosing.

3. An electro clamping vise as shwon in claim 1, wherein there are following parts on the drving seat of the guide screw rod: a set of driving motor having speed-reising gear case; big anc small gear sets which are coulat oh other; a driving seat and a connecting cover with a suitable positioning space; a key groove is installed on the rod side of guide screw rod in the shaft-direction, and is coupled with the screw hole of the driving seat; A square head part is shown at rod end for encasing the handle and for making manual rotation; A screw hole is installed facing to the guide screw rod, and the groove holes are located in the inner side and used for positioning the bearing in the shaft direction.A hole seat is installed just under the back screw hole for extending and positioning the speedreducing gear case of the driving motor, and the output shaft of the speed-reducing gear extends to the driving seat for driving the small gear; The speed-reducing gear case is installed at the front end of the driving motor; During the assembly, the speed-reducing gear case includinng driving motor itself can be buried in the groove holes of the driving motor.The driving seat is leant by the transverse convex plate extending from the speed-reducing gear and is fixed b the fixi piece; Big and small gear set is used for transfering the force of the driving motor to the guIde screw rod, in which the stall gear is installed on the output shaft of the speed-reducing gear case, and the big gear is installed penetrately on teh guide screw rod for coupling the small gear; The said big gear drives the guide screw rod by way of the key; The connecting cover is made as convex part upward in the middle of the basis of matching the configuration of the driving seat, and its two sides are made as flat plates, in which the convex part is used for leaning closely on the driving seat, and its two sides are locked on the bottom seat.

Moreover, a convex shaft with square handle is installed on the back side of the driving motor for providing manual operating handle driving; Furthermore, a touch switch is installed for controlling and stopping the back movement.

4. The further driving structure of the elctro clamping ives as described in claim 1 can be also a transverse driving motor, in which the guide screw rod is driven by the turbine rod and turbine wheel. The features of its structure are as follows: A shaft-directional key groove is installed on the guide screw rod and coupled with the screw hole of the driving seat; A screw hole is also installed at the penetrated position of the guide screw rod located relative to the driving seat; Its inner side has two stepped groove holes used for positioning the turbine wheel and shaftdirectional bearing.Another two-stepped hole is installed transversely at the lower end of the side of the said driving seat for penetrating the driving motor and the turbine rod; A speed-reducing gear case is installed at the front end of the driving motor, and the turbine rod is installed at the output end of the gear case. During the assembly, it is locked in the double stepped groove hole on the side of the driving seat by the positioning plate extending from the driving motor. A convex shaft of the hand wheel is installed on the convex back side of the motor for manual drive; The turbine wheel penetrated and coupled in the key groove of the guide screw rod by means of a key; The circumference of its lower end connects with the turbine rod to form a transmission structure.The shaft-directional bearings are installed on the two sides respectively; The connecting cover is installed on the inner side of the driving seat for pressing the shaft-directional bearing, so that the turbine wheel can be exactly positioned at the position of the coupling turbine rod; The main shaft of the driving motor can extent backward from the motor housing used for coupling and deriving as the said last section of the control.

5. An electro clamping vise as described in claim 1, wherein its driving structure can be further used for the clamping vise with the guide rod for positioning, in which a screw hole is installed on the bottom of the movable jowl for penetrating the guide rod.

It is driven and coupled by the driving motor with the gear set, so that it needs no shaft directional sliding between it and the guide screw rod and it connects with the other based on the transmIssion; There is no screw hole on the driving seat. There is only the penetrating hole used for the penetration.

It is similar to the conventional one, in which the end of the guide rod is small for putting the stopage bearing and for accepting the reverse action. It has a section of the screw thereads for putting encase ring and positioning screw nut. The big gear is couple with the guide screw rod and is not accepting and clamping the reverse action.

6. A clamping device according to claim 1 in which the motor drive circuit include a power supply providing a higher drive voltage for the motor during unclamping the that during clamping.

6. The motor of the electro clamping vise as described in claim 1, 2, wherin AC or DC motor can be driven by the selectable motor (such as series motor, in which the load current and stopping current has less difference and the motor has the larger magnetic winding) or the DC/AC driving motor is drIven by the its power supply.

7. The driving cirfuit of the electro clamping vise as described in claim 1-5 contains: a power supply equipment and can be DC or AC depending upon the kind of the motor; a switch of positive and reverse operation and stop.

It can be the push button with manual operative electric machine type or rotary switch. It is electric måchine type electromagnetic switch or electronic solid switch; DC/AC motor is used for the driving in positive or reverse direction.

8. The driving circuit of the electro clamping vise as described in claim 1-5 contains: DC or AC power source which can control the electric current, including the thermic bimetall type or comparative electric circuit type, and the current-limited type can be series crystal or phase gate fluid or power transformer; operating switch which can rotate positively and reversely, and which can accept manual or program control or another operation of electric current sign for driving directly the motor for raotating positively or reversely or indirect driving electric mahine type or electromagnetic switch or electronic solid relay for controlling the motor in positive or reverse rotation or stop; a motor used for AC and DC and for positive or reverse rotaion and it connects With the current control torque.

9. The driving circuit of the electro clamping vise as described in claim 1-5 contains: power supply equipment with largest current function, including the largest current is limited by the adjusting element for limiting the electric current; positive and reverse rotating switch and swtich equipemnt fro closing and opening the electric current, and used for controlling the positive or reverse rotation or stop of the motor; the motor can rotate positively or reversely to drive the machine.

10. The driving circuit of the electro clamping vise as described in claim 1-5 contains power source with limiting the largest output current used for driving the different positive and reverse rotation torque split phase motor and DC motor.

11. The driving equipment of the electro clamping vise as describe in claims 1-5. in which in the positive and reverse rotating switch circuit of a driving motor, the positive and reverse rotating switch is connected with damping rectance in series, when the motor drives positively the movable jowl (including fixed or adjustable resistor, electric induction element and capacitor) for limiting its torque less than which in the back loosing. The motor is a capacitor split phase driving single phase AC induction motor with a positive rotating input and reverse rotating input point, and the power source is a current source with limiting largest output current.

12. The further feature of the electro clamping vise as described in claims 1-5 is that the power source has double pressure feeding and is connected in seris with the output current; The switch is used for selecting the power source voltage and the rotating direction of the motor; It is a DC series motor. Using the change-over of the three positional switch, the DC motor is driven with positive clamping having less torque and with back reverse rotation having larger torque.

13. An electro clamping vise as described in claims 1-5. wherein the differnt torques in positive and reverse rotaion of DC motor can be also achieved by the change-over angleof the electric brush sloping with the change-over central line, based on the fact that different amature reactions during the positive and reverse rotations can generate the different torques.

Moreover, it can be also achieved by the wiring of double magnetization or by the differential double megnetization.

14. The driving motor of the electro clamping vise as described in claims 1-5, wherein the three phase induction driving motor can make Y-wiring advance clamping drive and Delta-wiring back loosing drive. Using a set of program current sign or manual operating electromagnetic switch (or hand switch), the electric circuit can be controlled in Y-positive rotation or Delta-reverse rotation. During Y-wiring advance, because Y-wiring rectance increases three times, the Y-wiring stop current can be selected as three times of Y-operating current. Therefore, the winding can not be burnt during the stopage for generating continuour clamping torque. Deltaback movement provides a larger back torque for loosing the movable jowl. Moreover, a limiting switch is installed at the end of back travel for safe positioning and stopage.Teh touch position of this switch and movable jowl can be changed by moving switch position or by adjusting the touch block of the movable jowl, so that it can provide a best economic back displacement during the mass production.

Amendments to the claims have been filed as follows CLAIMS 1. An electrically operated clamping device comprising a vice having a guide screw (1) drawn by an electric motor (3) , together with a drive circuit (801,802) for the motor, chacterised in that the motor and drive circuit are such that the torque developed by the motor at the beginning of unclamping is greater than that developed during clamping.

2. A clamping device according to claim 1 in which the motor is a d.c.-motor and the difference in torque is obtained by the brushes being inclined out of their central position.

3. A clamping device according to claim 1 in which the motor is a 3-phase a.c. motor, and is star-connected during clamping and delta-connected during unclamping.

4. A clamping device according to claim 1 in which the motor has separate windings for forWard and reverse operation.

5. A clamping device according to claim 1 in which the motor drive circuit includes an additional impedance during clamping.