Clamping apparatus

• US 4,771,999 A
• Filed: 07/30/1987
• Issued: 09/20/1988
• Est. Priority Date: 09/29/1986
• Status: Expired due to Term

• Current Assignee: Nitto Kohki Company Limited
• Original Assignee: Nitto Kohki Company Limited
• Inventors: Kazama, Yasuo, Takeuchi, Hirosato, Miyazaki, Osahiko, Kurihara, Naoya
• Primary Examiner(s): Watson, Robert C.
• Application Number:
  US07/079,412
• Time in Patent Office: 418 Days
• Field of Search: 269/134-138, 269/329, 269/285, 411/13
• US Class Current: 269/135
• CPC Class Codes: B25B 1/04 with pivoted jaws
• CPC Class Codes: B25B 1/10 using screws
• CPC Class Codes: B25B 1/24 Details, e.g. jaws of special shape, slideways
• CPC Class Codes: B25B 5/04 with pivoted jaws
• CPC Class Codes: B25B 5/10 using screws
• CPC Class Codes: B25B 5/16 Details, e.g. jaws, jaw attachments
• CPC Class Codes: F16B 31/025 with a gauge pin in a longitudinal bore in the body of the bolt
• CPC Class Codes: G01L 5/24 for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed

Abstract

In a clamping apparatus, a pressing member is moved on a base in a vertical and horizontal directions by rotation of a bolt. The bolt is provided with a longitudinal hole open end of which is covered by a window. A rod is placed in the hole so as to fix the inner end thereof to the inner end of the hole. A transparent holding member holding a colored fluid is sandwiched by the open side end of the rod and the window. When a tension stress is developed in the bolt, the open side end is far away from the holding member so that fluid covers the open side end.

Claims

1. A clamping apparatus for rigidly clamping a workpiece relative to a machine tool bed comprising:

a base block fixed to the top surface of the machine tool bed;

a pressing member having an end face located in a horizontally facing position relative to the top surface of the machine tool bed and disposed over the base block so that it is vertically movable relative to the top surface of the machine tool bed so as to positionally horizontally vary said end face relative to the workpiece;

a pressing bolt coupled to said pressing member and having an open ended longitudinally extending insertion hole, said pressing bolt having another end, opposite to said open end, threadably inserted into the base block and/or bed so the said pressing bolt is movable toward the base block and/or bed when it is rotated in one directon to responsively cause the pressing member to be moved, in said vertical direction, toward the base block and/or bed;

a rod placed within the longitudinally extending insertion hole of the pressing bolt and having an inner end portion fixed to the pressing bolt such that an end of said rod situated near the open end of the pressing bolt is relatively moved in a direction away from the open end of the pressing bolt toward the other end of said pressing bolt in response to a tension strain being exerted upon the pressing bolt;

a light transmissive window member fixed to and covering the open end of the longitudinally extending insertion hole of the pressing bolt; and

fluid holding means provided within said longitudinally extending insertion hole and directly behind a rear surface of the light transmissive window member and having a fluid which does not pass at least one portion of a light wavelength range, said fluid holding means causing a color change to be visibly perceived through said light transmissive window in response to the end of the rod situated on the open end side of the bolt being relatively moved away from said open end side of the pressing bolt in a direction toward the other end of said pressing bolt due to the exertion of a tension strain of a predetermined value upon the pressing bolt, which color change is caused by said fluid flowing into a space between said end of the rod and the rear surface of thelight transmissive window member; and

wherein,

said end of said rod near said open end of said insertion hole is painted with a relatively bright color or a light-reflective color, and wherein,

said fluid is of a dark color or a light-absorbing color in sharp contrast with the color of said painted end of said rod, and wherein,

said inner end portion of said rod is threadably inserted into said inner end portion of said longitudinally extending insertion hole of said pressing bolt, and wherein,

an end portion of said pressing member which is situated distant from said end face of said pressing member is rotatably coupled by a pin to said base block such that when it is rotated relative to said base block, said end face of said pressing member is displaced in said vertical and horizontal directions.

2. A clamping apparatus according to claim 1, wherein said fluid holding means is made of an elastic, light transmissive material and located between said light transmissive window member and said end of said rod such that said fluid holding means is so depressed by said end of said rod on the open end side of said pressing bolt as to be brought into intimate contact with the inner surface of said light transmissive window member, until said end of said pressing rod is relatively moved a predetermined distance from said open end side of said pressing bolt toward the inside of said insertion hole, whereby said fluid is displaced from a location between the end of said rod and the light transmissive window member.

3. A clamping apparatus for positionally clamping a workpiece relative to a bed of a machine tool, said apparatus comprising:

a first base block defining a receiving surface for receiving a portion of said workpiece and adapted to being rigidly attached to the bed of the machine tool;

a second base block;

a pressing member defining a forward end surface at one end thereof and being mounted at another end thereof to said second base block for pivotal movements between (i) a clamping position, wherein said forward end surface is in clamping contact with said workpiece so as to exert a clamping force of predetermined magnitude thereupon and thus positionally hold said workpiece between said forward end surface of said pressing member and said receiving surface of said first base block, whereby said workpiece is positionally clamped relative to said machine tool bed, and (ii) a released position wherein said forward end surface of said pressing member is separated from said workpiece to thereby release said clamping contact between said workpiece and said forward end surface;

said pressing member defining a bore near said forward end surface thereof;

said second base block defining a recess in opposition to a portion of said pressing member rearwardly of said defined bore thereof;

biasing means disposed within said defined recess and acting between said second base block and said portion of said pressing member for exerting a bias force upon said pressing member in a direction to assist its pivotal movement thereof from said clamping position towards said released position;

bolt means for rigidly coupling said second base block to said machine tool bed; and

clamping force adjusting/indicating means for permitting said clamping force to be selectively adjusted and for indicating when said predetermined magnitude of said clamping force has been attained, wherein said adjusting/indicating means includes;

(a) a pressing bolt having a head portion and a shank at least a portion of which is threaded, said shank being received within said defined bore of said pressing member and said threaded portion thereof adapted to being threadably coupled to said second base block and/or the machine tool bed such that said head portion thereof is in contact with said pressing member to pivotally move said pressing member between said clamped and released positions in response to turning movements being applied thereto;

(b) said pressing bolt establishing an axially elongate central hole having an open end at said head portion of said pressing bolt;

(c) an indicator rod rigidly received within said elongate central hole and defining an indicator surface at said open end thereof;

(d) a transparent window covering said open end of said elongate central hole;

(e) fluid holding means for containing a substantially opaque liquid between said indicator surface of said indicator rod and said transparent window;

(f) said indicator surface of said indicator rod normally pressing against said fluid holding means when said pressing member is in said released position and thereby effectively causing said fluid to flow to marginal regions within said fluid holding means so that said indicator surface is visibly perceptible through said transparent window;

(g) said indicator rod being relatively movable within said elongate central hole in a direction tending to separate said indicator surface from said fluid holding means in response to a tension force being exerted upon said pressing bolt when said pressing member is pivotally moved from said released position to said clamping position upon turning movement being applied to said head portion of said pressing bolt, which separation tendency of said indicator surface allows said fluid to flow from said marginal regions of said fluid holding means so as to create a fluid layer disposed between said indicator surface and said transparent window to thereby cause said indicator surface to become less visibly perceptible therethrough, which less visibly perceptible indicator surface is indicative of an increase in said clamping force being exerted upon said workpiece by means of said pressing member.

4. A clamping apparatus as in claim 3, wherein said indicator surface includes a painted layer.

5. A clamping apparatus as in claim 3, wherein said predetermined clamping force is indicated by means of said indicator surface not being visibly perceptible through said transparent window.

6. In combination with a machine tool having a bed, a clamping apparatus as in claim 3.